By law, Roy Perez should not have had a gun three years ago when he shot his mother 16 times in their home in Baldwin Park, Calif., killing her, and then went next door and killed a woman and her 4-year-old daughter. Mr. Perez, who pleaded guilty to three counts of murder and was sentenced last year to life in prison, had a history of mental health issues. As a result, even though in 2004 he legally bought the 9-millimeter Glock 26 handgun he used, at the time of the... (GunPolicy.org)