WASHINGTON (AP) — The gunman in the mass shootings at the Washington Navy Yard, Aaron Alexis, had a history of violent outbursts, was at least twice accused of firing guns in anger and was in the early stages of treatment for serious mental problems, according to court records and U.S. law enforcement officials.

But Alexis apparently managed to exploit seams in the nation’s patchwork of complicated gun laws designed to keep weapons out of the hands of dangerous people. He was able to buy a shotgun in Virginia with out-of-state identification, even though that would have prevented him from buying a handgun.