VIDEO: Police suspect neighbor bought weapons used in San Bernardino attack
Marquez allegedly purchased the two "assault-style" rifles over three years ago. Authorities haven't been able to talk to him because he checked himself into a mental hospital after the attack, a law enforcement official told The Associated Press.
Authorities with guns drawn raided Marquez's home in Riverside early Saturday, breaking windows and using a cutting torch to get into the garage, neighbors said.
FBI Director James Comey said the gun purchaser was "not a suspect, at least at this point."
Neighbors say Marquez lives in the Riverside home with his mother, stepdad and other siblings and that he mostly kept to himself.
MORE: These are the faces of the 14 killed in San Bernardino attack
Farook and his wife Tashfeen Malik used the two rifles, along with two handguns that the couple purchased, to kill 14 people at the Inland Regional Center during a holiday party.
The two were later killed in a gun battle between police about a mile away from the center.
VIDEO: Investigators say wife may have been driving force in San Bernardino rampage
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