Tom Calhoun described the gunman as a "thoughtful" and "introspective" guy.
A former high school classmate of 66-year-old James Hodkinson, who opened fire on the Republican baseball team during practice, says he was “shocked” when he learned who the gunman was.
Read: Democrats' Baseball Team Pictured Praying After Learning Republican Colleagues Were Shot
“I was totally shocked, was shaking for an hour,” Tom Calhoun told Inside Edition. “You never expect someone you know to do something like this, especially someone you knew and called a friend at one time in your life.”
After high school, Hodgkinson had multiple run-ins with the law: A DUI arrest in 1992 and a domestic battery arrest in 2006.
In March, he had another encounter with law enforcement when his neighbor, Bill Schaumleffel heard gunshots in his backyard.
“All of a sudden I see a man walk out from behind that shed and I could see he had a long gun or a shotgun or rifle and the shots he was shooting [were] really loud,” he told Inside Edition. “That's when I yelled at him and I said, ‘Hey! Stop shooting! There's houses over there!'"
Hodgkinson eventually complied when police asked him to stop firing.
Schaumleffel couldn't believe it when he learned his neighbor with the gun was the madman who tried to assassinate the Republicans.
Read: GOP Shooter Identified as Former Bernie Sanders Volunteer
“You read about these things in the paper and see things on the TV and here it was in our own backyard,” he said.
Hodgkinson was shot by a police officer in Wednesday morning's shooting and later died from his injuries.
Five people were shot and injured in the melee, including Congressman Steve Scalise, 51, who remains in critical condition.
Watch: Trump Speaks Out on Alexandria Shooting, Calls Rep. Scalise 'True Friend and Patriot'
