By Associated Press 8:38am, September 17, 2013 - Updated 8:42am, September 17, 2013
Essential personnel are allowed into the closed Washington Navy Yard in Washington. (AP Photo/Jacquelyn Martin)U.S. law enforcement officials say the Navy contractor identified as the gunman in the mass shootings at the Washington Navy Yard had been suffering a host of serious mental issues, including paranoia and a sleep disorder.
He also had been hearing voices in his head, the officials said.
Aaron Alexis, 34, had been treated since August by the Veterans Administration for his mental problems, the officials said. They spoke on condition of anonymity because the criminal investigation in the case was continuing. The Navy had not declared him mentally unfit, which would have rescinded a security clearance that Alexis had from his earlier time in the Navy Reserves.
Family members told investigators that Alexis was being treated for his mental issues.
Motive still a mystery
Investigators say the motive for Monday's mass shooting at Washington Navy Yard remains a mystery.
After law enforcement officers spent much of the day Monday looking for other possible gunmen, police now say they "feel comfortable" that the shooter acted alone.
He's been identified as Aaron Alexis, a 34-year-old defense contract employee and former Navy reservist. Twelve people were killed before police shot Alexis to death.
The shooting was the deadliest on a military installation in the U.S. since the tragedy at Fort Hood, Texas, in 2009.
Law enforcement officials say gunman Aaron Alexis carried three weapons at the Navy Yard: an AR-15 assault rifle, a shotgun and a handgun he took from an officer at the scene.
Senate returning to normal operations Tuesday
The Senate is returning to normal operations Tuesday following a shutdown due to the Navy Yard shootings.
Terrence Gainer, the Senate sergeant at arms, had restricted people from leaving or entering Senate buildings for part of the day Monday as authorities were searching for other potential shooters. Late Monday, however, authorities said they believed the gunman operated alone. Thirteen people, including the gunman, died in the shooting at the Navy Yard, about a mile south of the Capitol.
Gainer said that while operations are returning to normal, the U.S. Capitol Police will maintain a high level of security at the Capitol complex.
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