The picture emerging of the dead gunman in Monday 's rampage at the Washington Navy Yard is a study in contrasts , one of a man who practiced languages and meditated , and another of a cold-blooded killer . The gunman was identified as 34-year-old Aaron Alexis , a former Navy reservist and a current military contractor , the Washington FBI Field Office told CNN . His identity was confirmed by fingerprints and a picture ID card , the FBI said . Authorities have not released a possible motive in the morning shooting at the headquarters for Naval Sea Systems Command that left 12 people -- and the gunman -- dead . But a friend said Alexis was locked in a dispute over money with the company that contracted him to work for the Navy . Investigators also learned that Alexis had recently made contact with two Veterans Administration hospitals for apparent psychological issues , law enforcement sources told CNN on Tuesday . Authorities said earlier that they are confident that Alexis was the lone gunman , bringing to an end a daylong police search for a possible second suspect . Gaining access . Alexis was carrying a military-contractor ID that matched his appearance , a D.C. Metropolitan Police official told CNN on condition of anonymity . Alexis used that ID to gain access to the Navy Yard , according to a U.S. law enforcement official with knowledge of the investigation . He drove onto the installation and parked before walking a short distance to Building 197 . Once inside , according to the official , Alexis made his way to an overlook above the atrium and opened fire into the cafeteria . What is security like at Washington Navy Yard ? Initial reports said Alexis used an AR-15 semiautomatic rifle during the attack , but by Tuesday , law enforcement sources with knowledge of the investigation said that was not the case . It is believed that Alexis had rented an AR-15 , but returned it before Monday 's shooting , the officials said . Investigators have recovered three weapons from the scene , including a shotgun that Alexis is believed to have brought into the compound . The other two weapons -- handguns -- the sources say , may have been taken from guards . While the FBI was urging anyone with information about Alexis to come forward , investigators were focusing on reported incidents , including police run-ins , that portray a man with increasingly violent tendencies . Employment . Alexis was believed to have arrived in the Washington area last week , when he reportedly checked into a hotel , according to someone who met him at the hotel . The person , who declined to be identified , said Alexis indicated that he planned to be in the area for several weeks . Who are the victims ? At the time of the shooting , Alexis was working for The Experts , a subcontractor of HP Enterprise Services that was contracted to `` refresh equipment used on the Navy Marine Corps Intranet network , '' according to a statement released by the company . Alexis , who had Department of Defense security clearance , worked from September 2012 through January refreshing computer systems in Japan , said Thomas E. Hoshko , the CEO of The Experts . His security clearance was renewed in July to carry out the same type of contract work at the Navy Yard , Hoshko said . Alexis returned to work with The Experts that same month , he said . He worked at facilities in Rhode Island , North Carolina and Virginia for weeks at a time upgrading computer systems , Hoshko said . No one reported having any problems with Alexis during those assignments , the chief executive said . Alexis began working at the Navy Yard last week , though it was unclear whether he had actually begun working or was still securing his base clearance , Hoshko said . Many surprised . There were no indications that Alexis had any ideological differences with the Navy or any disagreements with anyone at the Navy Yard , the U.S. law enforcement official said . Alexis ' family reeled at the news that he was believed to be the man behind the killings . `` What I do know is he was n't that type of person , '' Anthony Little , who identified himself as Alexis ' brother-in-law , told reporters outside his Brooklyn , New York , home . `` I did n't really hear anything that would make me feel , as a newcomer to the family , that somebody should be watching him . '' He said the family 's initial reaction was `` very distraught , very stressed out , tears . '' `` You know , they did n't see it coming , '' said Little , who is married to Alexis ' sister Naomi . `` Their hearts are going out more to the victims and the people that got hurt because , you know , there 's more lives lost and we do n't need that right now . We really do n't . '' Opinion : What could have prevented Navy Yard carnage ? Navy reservist . Alexis , who was from New York City , served as a full-time Navy reservist between 2007 and 2011 , according to military records . In the Navy , he achieved the rank of aviation electrician 's mate 3rd class , working on aircraft electrical systems , the records show . Alexis was honorably discharged after a `` pattern of misconduct , '' a U.S. defense official with knowledge of the investigation told CNN on condition of anonymity . The official did not detail the misconduct . Most recently , Alexis worked as an information technology contractor with the Navy , Secretary of the Navy Ray Mabus told CNN 's Wolf Blitzer . Legal run-ins . Alexis appeared to have had sporadic run-ins with the law , dating back to at least 2004 when he was arrested in Seattle , accused of shooting out the tires of a man 's truck in an anger-fueled `` blackout , '' according to a Seattle Police Department report . He told investigators he believed the man , a construction worker , was mocking him , but had no memory of shooting out the tires , the report said . Investigators later spoke with Alexis ' father , who told police that his son had anger management problems associated with post-traumatic stress disorder , which he suffered after working `` as an active participant in rescue attempts '' during the September 11 , 2001 , terrorist attacks in New York , the report said . Alexis was arrested in August 2008 on a charge of disorderly conduct in DeKalb County , Georgia , county police said Tuesday . And in 2010 , Alexis was arrested by Fort Worth , Texas , police but never charged over an allegation that he fired a gun through the ceiling of his apartment . According to records , he told police he accidentally fired it while cleaning it . Witness : `` He aimed his gun at us '' Good friends . His last known address was outside of Fort Worth , where he was roommates for three years with Nutpisit Suthamtewakul , who described Alexis as his best friend . Alexis befriended Suthamtewakul four years ago after he emigrated from Thailand . Alexis taught him about American culture , Suthamtewakul told CNN . Alexis , he says , was fluent in Thai and attended a Buddhist temple . When Suthamtewakul opened the Happy Bowl Thai Restaurant , Alexis would occasionally help out , waiting tables , he said . The two were roommates until five months ago , when Suthamtewakul got married and Alexis had to move out . Toward the end , Alexis spent a lot of time holed up in his room , keeping to himself , Suthamtewakul said . On Monday , Suthamtewakul was stunned by the news that Alexis was said to be the shooter in the rampage at the Navy Yard . `` I ca n't believe he did this , '' he said . `` He never showed any sign of violence . '' Frustrations . But there were signs that Alexis was unhappy . He was having a hard time trying to get on his feet , said Suthamtewakul 's wife , Kristi . He helped out at the restaurant but not for pay . `` He was using this as an educational experience to help learn Thai , '' she said . He enjoyed making deliveries to homes , where the language was spoken . He talked about moving to Thailand . But to Suthamtewakul , Alexis seemed `` frustrated with life . '' She is grieving . `` He was like one of our best friends , like a brother to us and always willing to go out of his way to help us out with things . '' He was very frustrated with the company that contracted him to work for the Navy , according to another friend . Alexis claimed he was n't paid properly by the company after returning from a months-long assignment to Japan last year , said Michael Ritrovato , another former roommate . It was unclear whether the dispute was over salary or expenses . Alexis just felt the company owed him money and had not paid him , Ritrovato said . Gun knowledge . He is in shock over his friend 's actions . `` He was an easygoing guy . I do n't know of any reason for this , '' he said . But Ritrovato knew Alexis was fascinated by guns . `` He was ... knowledgeable with military rifles and handguns . At least he led us to believe he was . But nobody ever had the idea that he would use them in a derogatory way , '' he said . It is not clear whether Alexis was still living in Fort Worth area at the time of the shooting .
A friend says Alexis was frustrated with life . He had been in a relationship for about two years He used a contractor ID to access the Navy Yard , an official says . Alexis claimed he was n't paid by his employer , a friend says .