Connecticut authorities on Monday released a summary of their long-awaited report on last year's tragic shooting at Sandy Hook Elementary School, an investigation that lasted nearly a year yet frustratingly (yet not unexpectedly) leaves the major question—that of Adam Lanza's likely motive—unanswered.

"The obvious question that remains is: 'Why did the shooter murder twenty-seven people, including twenty children?', state attorney Stephen Sedensky writes in the just-released executive summary. "Unfortunately, that question may never be answered conclusively, despite the collection of extensive background information on the shooter through a multitude of interviews and other sources. The evidence clearly shows that the shooter planned his actions, including the taking of his own life, but there is no clear indication why he did so, or why he targeted Sandy Hook Elementary School."

Reporters (including myself) are still picking through the document (you can do the same below). In the meantime, here are a few of the key sections that shed some light on both Lanza and the heartbreaking events of Dec. 14, 2012.

Adam Lanza's "significant" mental heath issues:

It is known that the shooter had significant mental health issues that affected his ability to live a normal life and to interact with others, even those to whom he should have been close. As an adult he did not recognize or help himself deal with those issues. What contribution this made to the shootings, if any, is unknown as those mental health professionals who saw him did not see anything that would have predicted his future behavior.

His physical size: "The shooter, age 20, was 72 inches tall and weighed 112 pounds."

His "obsession" with Columbine:

He had a familiarity with and access to firearms and ammunition and an obsession with mass murders, in particular the April 1999 shootings at Columbine High School in Colorado. Investigators however, have not discovered any evidence that the shooter voiced or gave any indication to others that he intended to commit such a crime himself. ...

While the vast majority of persons interviewed had no explanation for the shooter’s actions, a review of electronic evidence or digital media that appeared to belong to the shooter, revealed that the shooter had a preoccupation with mass shootings, in particular the Columbine shootings and a strong interest in firearms. For example, there was a spreadsheet with mass murders over the years listing information about each shooting.

The weapons he used, and those he didn't:

The following weapons were recovered in the course of this investigation: (1) a Bushmaster Model XM15-E2S semi-automatic rifle, found in the same classroom as the shooter’s body. All of the 5.56 mm shell casings from the school that were tested were found to have been fired from this rifle. (2) a Glock 20, 10 mm semi-automatic pistol found near the shooter’s body and determined to have been the source of the self-inflicted gunshot wound by which he took his own life. (3) a Sig Sauer P226, 9 mm semi-automatic pistol found on the shooter’s person. There is no evidence this weapon had been fired. (4) a Izhmash Saiga-12, 12 gauge semi-automatic shotgun found in the shooter’s car in the parking lot outside the school, and which was secured in the vehicle’s trunk by police responding to the scene. There is no evidence this weapon had been fired. (5) a Savage Mark II rifle found at 36 Yogananda Street on the floor of the master bedroom near the bed where the body of the shooter’s mother was found. This rifle also was found to have fired the four bullets recovered during the autopsy of the shooter’s mother.

All the weapons—and ammo—were bought legally by his mother:

All of the firearms were legally purchased by the shooter’s mother. Additionally, ammunition of the types found had been purchased by the mother in the past, and there is no evidence that the ammunition was purchased by anyone else, including the shooter.

His first Sandy Hook victims, and a possible lucky break:

Just down the hallway from the main office, in the direction that the shooter was to be seen firing, a 9:30 a.m. Planning and Placement Team (PPT) meeting was being held in room 9, a conference room. It was attended by Principal Dawn Hochsprung and School Psychologist Mary Sherlach, together with a parent and other school staff. Shortly after the meeting started, the attendees heard loud banging. The principal and school psychologist then left the room followed shortly after by a staff member. After leaving the room, Mrs. Hochsprung yelled “Stay put!”

As the staff member left the room, the staff member heard gunshots and saw Mrs. Hochsprung and Mrs. Sherlach fall down in front of the staff member. The staff member felt a gunshot hit the  staff member’s leg. Once down, the staff member was struck again by additional gunfire, but laid still in the hallway. Not seeing anyone in the hallway, the staff member crawled back into room 9 and held the door shut. A call to 911 was made and in the ensuing moments the telephone in room 9 was also used to turn on the school wide intercom system. This appears to have been done inadvertently, but provided notice to other portions of the building.

The two classrooms:

Classroom 8’s substitute teacher was Lauren Rousseau, age 30, who was assisted by Rachel D’Avino, age 29, a behavioral therapist. Fifteen children were found by police. Fourteen who were deceased and one who was transported to Danbury Hospital and later pronounced dead. The two adults were found deceased close to the children. In all, seventeen people were killed in classroom 8. A sixteenth child survived and exited classroom 8 after the police arrived.

Classroom 10’s teacher was Victoria Soto, age 27. Working with her was Anne Marie Murphy, age 52, a behavioral therapist. Five children were found, with Mrs. Murphy partially covering one child. Four of the five children were deceased. One of the five children was transported to the hospital and pronounced dead. Miss Soto was found deceased in the room near the north wall with a set of keys nearby. Nine children had run out of the room and survived. A police officer found two uninjured children in the class restroom.

The what-if moment from earlier in the day:

Sometime on the morning of December 14, 2012, before 9:30 a.m., the shooter shot and killed his mother, Nancy Lanza, in her bed at 36 Yogananda Street, Newtown. The weapon used was a .22 caliber Savage Mark II rifle. Someone in the area reported hearing “two or three” gunshots in the neighborhood between 8:00 a.m. and 9:00 a.m. That person thought them to be from hunters, though the person indicated the shots did “sound unusually close.”

Lanza's room, and his damaged hard drive:

The shooter’s second floor bedroom windows were taped over with black trash bags. The second floor computer room also had its windows covered. There, investigators found a computer hard drive that appeared to have been intentionally damaged. To date, because of the extensive damage, forensic experts have not yet been able to recover any information from that hard drive.

In a typical criminal case, the investigation would remain open when potentially important evidence was still being examined. Given the improbability of any information being recovered from the damaged hard drive, this outstanding piece of evidence is not preventing the closure of this case now. Should any relevant information related to the existence of any accessory or co-conspirator be obtained from the hard drive, the case will be reopened.

Other items found in his room:

A Christmas check from the mother to the shooter to purchase a CZ 83 firearm; A New York Times article from February 18, 2008, regarding the school shooting at Northern Illinois University; Three photographs of what appear to be a dead human, covered in blood and wrapped in plastic; The book Amish Grace: How Forgiveness Transcended Tragedy, Jossey-Bass, 2007, by Donald B. Kraybill, Steven Nolt and David Weaver-Zercher; and Photocopied newspaper articles from 1891 pertaining to the shooting of school children.

And on his computer (many of which the investigators concede may have no relevance to the case):

- Bookmarks pertaining to firearms, military, politics, mass murder, video games, music,
books, Army Ranger, computers and programs, ammunition, candy, economic books
- Web page design folders
- Two videos showing suicide by gunshot
- Commercial movies depicting mass shootings
- The computer game titled “School Shooting” where the player controls a character who enters a school and shoots at students
- Screen shots (172) of the online game “Combat Arms”
- “Dance Dance Revolution” (DDR) game screen shots
- Videos of shooter playing DDR
- Images of the shooter holding a handgun to his head
- Images of the shooter holding a rifle to his head
- Five-second video (dramatization) depicting children being shot
- Images of shooter with a rifle, shotgun and numerous magazines in his pockets
- Documents on weapons and magazine capacity
 - A document written showing the prerequisites for a mass murder spreadsheet
- A spreadsheet listing mass murders by name and information about the incident
- Materials regarding the topic of pedophilia and advocating for rights for pedophiles (not child pornography)
 - Large amount of materials relating to Columbine shootings and documents on mass murders
- Large amount of materials on firearms
- Comedy videos
- Music
- Images of hamsters
- Images of Lego creations

Lanza's love of "Dance Dance Revolution":

The shooter liked to play a game called “Dance Dance Revolution” (DDR), which is a music video game in which the player stands on a platform, watches a video screen and moves his feet as directed by the video. A home version of this was seen and photographed in the shooter’s home. Several videos of him playing DDR were found on digital media taken from the home.

The GPS found in the home and reportedly belonging to the shooter indicated that he regularly went to the area of a theater that had a commercial version of the DDR game in the lobby. In 2011 and up until a month before December 14, 2012, the shooter went to the theater and played the game. He went most every Friday through Sunday and played the game for four to ten hours.

An acquaintance of the shooter from 2011 to June 2012 said that the shooter and the acquaintance played DDR quite a bit. They would play the game and occasionally see a movie. They did not play first person shooter games at the theater. The shooter had stamina for DDR and never appeared winded unless really exhausted.

Lanza as a relatively normal kid:

The acquaintance [with whom Lanza played Dance Dance Revolution] said the shooter seemed to enjoy nature and mentioned the possibility of going hiking more than once. The shooter was capable of laughing, smiling and making jokes, though always in a dry fashion. The shooter never mentioned being bullied while growing up. Topics of conversation included world and current events, and included chimpanzee society and how they interacted.

Bullying:

Both the shooter’s mother and father indicated that the shooter was bullied growing up. The father indicated that it was not excessive and concerned his social awkwardness and physical gait. [But] ... other witnesses did not recall the shooter being overtly bullied. Nonetheless, the shooter appears to have had few friends growing up.

His relationship with his father:

The shooter’s father saw him regularly until he turned 18. They would go hiking, play video games and other activities. They went shooting twice. The shooter had a cell phone but never used it. Calls all went to voice mail. His father would just e-mail him when he wanted to reach him.

The shooter’s relationship with his father deteriorated in the last quarter of 2010 and the father last saw the shooter in that year. After that the father would reach out to the shooter by mail or through e-mails regularly, asking him to join him at various places for different activities. The shooter stopped responding at some point prior to December 2012.

With his brother:

After college, the brother moved out of state. He reached out to the shooter a few times but the shooter did not respond. As of December 14, 2012, the older brother had not had contact with the shooter since 2010. The brother believed that the shooter and his mother had a close relationship. After his older brother left for college, the shooter reportedly became interested in firearms and at one point considered joining the military.

With his mother:

The mother took care of all of the shooter’s needs. The mother indicated that she did not work because of her son’s condition. She worried about what would happen to the shooter if anything happened to her.

One witness indicated that the shooter did not have an emotional connection to his mother. Recently when his mother asked him if he would feel bad if anything happened to her, he replied, “No.” Others, however, have indicated that they thought the shooter was close to his mother and she was the only person to whom the shooter would talk.

A person who knew the shooter in 2011 and 2012 said the shooter described his relationship with his mother as strained because the shooter said her behavior was not rational

I'll continue to update with any other noteworthy nuggets as I find them. In the meantime you can take your own look here:

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This post has been updated.