During his stint in the Navy, Alexis exhibited a pattern of misconduct that included eight to 10 infractions, ranging from a traffic violation to unexcused absences, according to a Navy official. There was also an arrest in 2010 for firing his gun through a neighbor's floor. He claimed it was an accident and was not prosecuted, according to the district attorney's office in Tarrant County, Texas.
And one person close to Alexis said she suspects he repaid her kindness with mischief.
Kristi Suthamtewakul told ABC News that she was convinced that Alexis poured sugar into her new Honda Accord, even though she let him to live in her home and work at her restaurant. Suthamtewakul said Alexis had become frustrated when she was unable to drive him to job interviews and to buy groceries.
But Suthamtewakul's husband, Nutpisit, said there was no way Alexis was capable of shooting innocent people.
"He's not aggressive," Nutpisit Suthamtewakul, a friend and former roommate of Alexis's, told ABC News. "He had a gun, but that doesn't mean he's going to shoot people. He had a concealed-weapons permit."
Nutpisit Suthamtewakul said Alexis liked to play games, drink and party. Alexis spoke Thai fluently, he said, traveled a lot for work and had been living in Washington for four or five months.
"I don't believe he did that," Suthamtewakul said. "He can be tough physically, but I don't think he'd kill people."