SINGAPORE - For some, 34-year-old Aaron Alexis was a gentle young man who taught himself to speak Thai for his earlier job as a waiter, and he would chant Thai prayers at a Buddhist temple.
"There was nothing sinister about him," said Ms Kristi Suthamtewakul, 35, who helps run her family's Thai restaurant outside Fort Worth, Texas, where Alexis worked as a waiter and deliveryman, The Los Angeles Times reported.
Alexis, a former Navy electrician's mate working as a government subcontractor, was shot dead by police after he killed 12 people at the Washington Navy Yard on Monday, authorities said.
Ms Suthamtewakul recalled Alexis celebrating Christmas and New Year's with her and her husband Nutpisit, and singing "(I Can't Help) Falling In Love With You" at a karaoke bar.
Alexis was generally easy-going, she said in an interview at the restaurant, the Happy Bowl. But he bristled when describing his service in the Navy and the benefits he believed had been withheld.
Mr Suthamtewakul said Alexis drank alcohol, always carried a gun and "acted childish - not like a 34-year-old".
Others had difficult encounters with Alexis. A Fort Worth resident described him as a brooding, menacing figure quick to brandish and fire a gun.
Alexis was investigated by police in Fort Worth and Seattle for firing a handgun in incidents involving disputes with a neighbour and a construction worker.
He also had a string of Navy disciplinary infractions leading up to his discharge in January 2011.
But there was little indication from his public record that he was capable of escalating from petty disputes to a mass shooting.
A woman who lived at the flat above Alexis' told police in September 2010 that he had harangued her about supposed noises from her apartment and confronted her in the carpark.
Police said Alexis fired a shot into the woman's floor from his apartment. He told police his handgun had gone off as he was cleaning it, but the woman said she thought the shooting was deliberate.
"She is terrified of Aaron and feels this was done intentionally," a police report said.
In Seattle in 2004, a construction worker told police that Alexis had stared at him and fellow workers every day for a month, occasionally brandishing a handgun, at a construction site next to his residence.
The worker said he had never spoken to Alexis, who fired three shots from a handgun into the worker's parked car in May 2004.