Authorities said Aaron Alexis, 34, of Fort Worth is the dead gunman.
WASHINGTON -- On the surface, Aaron Alexis' time in the Navy appears to have been routine.
But as word spread Monday that Alexis is suspected of gunning down a dozen people at the Washington Navy Yard here, Navy officials who asked not to be identified said the 34-year-old veteran had a pattern of misconduct.
That pattern appears to have contributed to two prior shooting incidents in Seattle and Fort Worth -- seemingly minor incidents that damaged a car and an apartment but resulted in no injuries.
What may have caused Alexis to go on a deadly shooting spree Monday morning remained a mystery to FBI and Navy officials, as well as acquaintances of the quiet man who split his time in recent years between Texas, New York and Washington State.
Alexis was working most recently for a company called "The Experts," a subcontractor on an HP Enterprise Services contract to refresh equipment used on the Navy Marine Corps Intranet network. A federal law enforcement official said he was living at a Residence Inn in Southwest Washington.
The official, who is not authorized to comment publicly, said Alexis purchased at least some of the weapons used in the assault within the past few days in Virginia. Then on Monday, he allegedly drove to the Navy Yard complex and cleared security checkpoints before parking in a lot on the property.
It is believed that Alexis was involved in two altercations in which he opened fire, killing one or possibly two people. The official said Alexis then entered the building and proceeded to the third and fourth floors, where much of the assault was carried out.
The official said it wasn't apparent that Alexis was targeting specific people, but that he apparently planned his actions in advance.
Valerie Parlave, chief of the FBI's D.C. field division, appealed for the public's help to assist in providing information about the shooter's actions and movements prior to the attack. The FBI posted his photographs on its website.
Navy Secretary Ray Mabus told CNN that Alexis was serving as an information technology contractor at the time of the shooting. He had enlisted in the Navy in 2007 and attained the rank of Aviation Electrician's Mate 3rd Class.
From 2008 to 2011, Alexis served with Fleet Logistics Support Squadron 46 at the Naval Air Station in Fort Worth. He lived in that area and was arrested at least once in 2010 for firing a gun through the ceiling of his apartment. He told police it had been an accident.
The Tarrant County District Attorney's Office issued a statement Monday saying that no charges were pursued against Alexis. "It was determined that Alexis was cleaning a gun in his apartment when it accidentally went off,'' Tarrant County District Attorney Joe Shannon Jr., said. "No one was injured.''