The official, speaking on condition of anonymity to discuss the current investigation, also said that in addition to his two previously known arrests in 2004 and 2010, Alexis had been arrested in DeKalb County, Ga., in 2008 on a disorderly conduct charge and held for two nights.
None of the disciplinary problems or his arrests, however, prevented Alexis from receiving a security clearance or from purchasing a shotgun recently in northern Virginia.
The Navy gave Alexis an administrative punishment after his 2008 arrest. Officials have not revealed what punishments Alexis received for his other offenses, but sanctions often range from loss of pay to reduction in rank.
Alexis applied in 2011 for an early discharge from the Navy, before his enlistment was up. Because of the spate of disciplinary problems, Navy officials looked at giving him a general discharge, which is given to sailors with conduct problems whose performance otherwise is satisfactory. But after examining his record closely, they opted to give him an honorable discharge in January 2011, the official said.
The additional evidence regarding Alexis' disciplinary history came as officials also disclosed that he recently had sought treatment at a veterans healthcare facility for mental problems.
Alexis "went to the VA to talk to them about mental-health issues. He was trying to get help, we think," said a federal official, also speaking on condition of anonymity to discuss the investigation.
He had been hoping to get back into the Navy but was "experiencing problems" at the contracting firm that employed him, the official said.
Alexis "didn't take that very well," the official added.
Investigators have confirmed that Alexis bought the shotgun used in Monday's shooting at a gun shop in Lorton, Va. Managers at the store, Sharp Shooter, referred questions to their lawyers.
Three weapons were found near Alexis' body Monday — the shotgun, a semiautomatic rifle and a pistol. Investigators are looking at the possibility that he may have seized one or more of the weapons from a security guard he shot at the base.
Investigators are also looking at the possibility that Alexis may have nursed a grievance with his employer regarding pay.
Thomas Hoshko, chief executive of the firm the Experts, said he wasn't aware of reports of a pay dispute or that Alexis may have sought treatment for mental illness. Alexis had held a security clearance since 2007, when he joined the Navy, Hoshko said.
Alexis had worked for the company on a contract in Asia last year and had recently been rehired and assigned to work at the Navy Yard. He had "no personal or professional issues," Hoshko said in an email.
Hoshko added that Alexis passed a background check in July and a drug test. He received an identification card from the
"No one who conducted his background investigations made us aware of any potential issues with mental health," Hoshko said.
Both the Defense Department and the Diplomatic Security Service had "reviewed a drug test and two background checks on Alexis," including one in July, before his assignment to the Navy Marine contract, he added.
Alexis returned to the firm in July after telling a colleague, he needed "to get back to work" because "school did not pay," Hoshko said.
Hoshko added that Alexis "successfully completed over six short-term assignments" at various military installations "prior to being assigned to the Washington Navy Yard last week."
"We were not aware of any problems regarding his personal or professional work prior to this most unfortunate incident," he said.
The company is a subcontractor for