Robert Card, the suspect in mass shootings in Maine, is an Army reservist.
He began acting erratically months ago while training at West Point in New York, according to a military official.
The military says Card threatened other soldiers with violence, forcing police to take him in for a mental evaluation.
"And I'm sure there will be a lot of review of this. And a lot of analysis. Was there something missed? Was he teamed deemed a danger to himself or someone else?" said Maine Sen. Angus King.
The Army confirmed Card had been a reservist for more than 20 years, starting in December 2002. He was listed as a petroleum supply specialist and was never deployed to combat.
"This city did not deserve this terrible assault on its citizens, on its peace of mind or its sense of security," said Maine Gov. Janet Mills.
Card was honored multiple times in his military service, with medals including the Humanitarian Service Medal, awarded to people who participate in a significant military act or act of humanitarian nature.
Search warrants executed, but Maine shootings suspect still on run
Robert Card was officially named a suspect in the Lewiston shootings and is considered armed and dangerous.
