The Bushmaster M4 Types Carbine, a semiautomatic rifle, uses a 20 or 30-round magazine.

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Three guns were recovered near the gunman's body: a Glock, a Sig Sauer and a .223 Bushmaster rifle.

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The rifle is a Bushmaster version of a widely made AR-15, the civilian version of the M-16 rifle used by the U.S. military.

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The shooter's mother, Nancy Lanza, bought the Bushmaster firearm two years ago at Riverview Gun Sales, according to Detective Matthew Carl of the East Windsor Police Department.

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Wilson said the gun used in the crime was likely a .22 caliber handgun, different from the Bushmaster .223 rifle thought to be used in the D.

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The offer, capping six months of negotiations between the Department of Economic and Community Development and Freedom Group, was dropped after private equity firm Cerberus Capital Management announced it would sell Freedom Group, manufacturer of the Bushmaster AR-15.

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Weapons like the Bushmaster mimic the appearance and some features of fully automatic military rifles, though they technically do not meet the definition of an assault weapon because they are semi-automatic -- meaning each shot requires a trigger pull.

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The assault weapons ban was a complicated law and even firearms like the .223 Bushmaster believed used by the gunman Friday, wouldn't necessarily have been illegal under that law, said Jonathan Lowy, director of the legal action project at the Brady Center to Prevent Handgun Violence.

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