Federal investigators were seen on Thursday outside the home of California bar shooting suspect Ian David Long.
Neighbors described the man who shot and killed 12 people at a country music bar as distant in public but combative with his mother inside the suburban Los Angeles home the two shared.
Long joined the Marines at 18 and was married as a 19-year-old in Honolulu in June 2009, according to military and court records.
His military service lasted nearly five years, and he was honorably discharged with the rank of corporal in 2013, the Pentagon said. He was part of the infantry, responsible for hauling and shooting machine guns.
During his service, Long's marriage fell apart. He and his wife separated in June 2011, while he was deployed on a seven-month tour in Afghanistan. The couple cited irreconcilable differences in divorce papers filed in May 2013, two months after Long left the Marines.
Later, he enrolled at nearby California State University, Northridge, last attending in 2016, the school said in a statement.
More recently he was living in a home where neighbors said they could hear frequent, aggressive shouting between Long and his mother, especially over the last year.