CHATTANOOGA, Tenn. (WJZ) — Authorities are honing in on the mindset of the man who killed four marines and wounded three other people at military facilities. They’re looking into a trip the shooter took overseas, and who he met while he was there.

Christie Ileto with a closer look at the gunman.

READ MORE: Star Spangled Celebration: Fourth Of July Fireworks Light Up Baltimore's Skyline Once Again

Muhammad Abdulazeez was described as an all-American student from a well-to-do family. So how did he become an unsuspecting killer?

The feds are scrambling to piece together why Muhammad Youssef Abdulazeez opened fire at two armed service recruiting centers, killing four marines. It’s being called an act of domestic terrorism.

“My judgment and my experience is that this was an ISIS inspired attack,” one official said.

Though there’s been no confirmed link made to the terror group, authorities are desperate to discover–is there enough ISIS propaganda online to motivate Abdulazeez to do this? Or was he radicalized on his seven-month visit to the Middle East?

The answers could be in the seized cell phone and computer from his Tennessee home.

A blitz of gunfire with cops ends his half hour killing spree. But three days before, Abdulazeez, a practicing Muslim, writes in his online blog: “This life is short and bitter,” and the time to “…submit to Allah might pass you by.”

READ MORE: Bacteria Levels Prompt Recreational Water Advisory At Cox's Point Park

“That is not Islamic. It has nothing to do with Islam,” said Col. Rudwan Abu-Rumman, Anne Arundel County Muslim Council.

The massacre happened on the last day of Ramadan. Muslim communities in Maryland condemn the senseless violence and don’t want the public to jump to conclusions.

“Even though it has not been linked to ISIS or the faith, you still put yourself on the defensive?”

“Because the perpetrator’s name is Muhammad and he is believed to be Muslim. And so just by that, by virtue of that association, there is a very real fear there is going to be backlash against the Muslim community,” said Zainab Chaudry, CAIR.

But the mystery is how did someone once described by peers as an all-American kid morph into an unsuspecting terrorist?

MORE NEWS: Mother Of Abandoned Newborn Receives 18-Month Sentence

Court records show the 24-year-old had no prior run-ins with the law, except for an April DUI.