From USA Today:
Early Monday morning, William Spengler Jr., 62, set fire to his house and a car, hid behind a berm with a Bushmaster .223 rifle, a Mossberg 12-gauge shotgun and a .38-caliber Smith & Wesson pistol and fired on the first responders from West Webster, N.Y., a Rochester suburb. As firefighters ran for cover and evacuated the neighborhood, the fire spread to six other houses and Spengler fatally shot himself, Webster Police Chief Gerald Pickering said.
Police are still trying to piece together exactly what happened in western New York on Christmas Eve, but they now say that it was that first gun—the Bushmaster .223 rifle—that Spengler most likely used to kill two volunteer firefights from long range and seriously wound two others on Christmas Eve, according to the New York Times.
If the name of that gun sounds familiar it is because it was the same make and caliber weapon that authorities say Adam Lanza used to kill 20 children and six adults at Sandy Hook Elementary in Newtown, Conn. on Dec. 14. Before that tragedy, the semi-automatic weapon also made headlines as one of the weapons allegedly brandished by James Holmes, who opened fire at a movie theater in Colorado this summer, and Jacob Tyler Roberts, who reportedly did the same at an Oregon shopping mall earlier this month. It was also the weapon of choice for John Allen Muhammed and Lee Boyd Malvo during the so-called Beltway Sniper Shootings of 2002.
Time magazine laid out the gun's history earlier this year:
The AR-15 rifle was first developed by the Fairchild ArmaLite corporation in 1957. ArmaLite sold the rights to the design to Colt in 1959, and the weapon was adapted for military use as the M16; it went in to service in Vietnam in 1963. The modern AR-15 is a demilitarized version of the M16, and is now manufactured by several companies including Bushmaster, Colt and ArmaLite. It is a lightweight, small-caliber semi-automatic rifle, with a light recoil and a variety of optional barrel lengths and targeting/aiming devices. ... Depending on the make, model and options, an AR-15 can cost anywhere from $900 to $2000. ...
Bushmaster, based in Madison, N.C., was founded in 1973 by Richard Dyke, who sold the company to Cerebrus Capital Management in 2006 .... It’s currently part of the Freedom Group, a conglomerate of arms manufacturers whose 13 brands also include Remington, Marlin Firearms, and DPMS/Panther. In 2011, the company had sales of $775 million, according to its annual report, and sold 1.1 million rifles and 2 billion rounds of ammunition.
In the wake of Newtown and in the midst of mounting public pressure, Cerberus announced earlier this month that it plans to sell off Freedom Group, saying that the Sandy Hook shooting represented "a watershed event that has raised the national debate on gun control to an unprecedented level."
The AR-15 is normally one of the first guns name-dropped by gun control advocates discussing the weapons they're most concerned about. Despite that (or maybe partly because of it) the gun also remains one of the most popular semi-automatic rifles on the market. According to an estimate by Guns and Ammo magazine from March, gunmakers manufactured roughly 1.5 million of the rifles in the past five years alone.
Updated at 11:25 a.m. to make citations more clear.