Chattanooga, Tennessee (CNN) The man who killed four U.S. Marines and a Navy sailor in Chattanooga, Tennessee, had changed after spending time in the Middle East and "distanced himself" for the first few months after returning, a friend says.

"Something happened over there," Abdulrazzak Pirzada said of Muhammad Youssuf Abdulazeez, adding that "he never became close to me like he was before he went overseas. ... I'm sure he had something that happened to him overseas."

Jordanian sources said Abdulazeez had been in Jordan as recently as 2014 visiting an uncle. He visited Kuwait and Jordan in 2010, Kuwait's Interior Ministry said.

Abdulazeez had guns, Pirzada said, and would go shooting as a hobby. When the childhood friends saw each other last weekend at the Islamic Society of Greater Chattanooga, Abdulazeez was his normal self and was positive, Pirzada said.

Pirzada, a Chattanooga resident, was shaken and holding back tears as he spoke to CNN, saying his friend was "the coolest guy" who "was always so positive about people."

"Whatever caused this to happen, it's not him, it's not normal. That's not how he is," Pirzada said.

People who knew Abdulazeez were stunned to hear he was the man who sprayed a military recruiting center at a strip mall with bullets, then drove seven miles to assault Navy Operational Support Center Chattanooga. He killed a sailor and four Marines, and wounded two more people, before being killed by police.

Friends described Abdulazeez as a once-devoted, disciplined mixed-martial-arts fighter; a top student known for smarts, charm and humor; and a devout Muslim who kept in touch with his roots in the Middle East.

The FBI hasn't released much information on Abdulazeez, saying it doesn't yet know what motivated the bloodshed but it is working on an assumption. "We will treat this as a terrorism investigation until it can be determined that it is not," FBI Special Agent Edward Reinhold said.

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'National security alerts' joke

Abdulazeez was born in Kuwait in September 1990, during the Iraqi invasion of that country, Kuwait's Interior Ministry said. The ministry didn't explain how Abdulazeez came to be born there but said he holds Jordanian citizenship.

Jordanian sources, however, denied that he was a Jordanian citizen, but rather a Palestinian who carried a Jordanian travel document. The sources said he was born Mohammad Youssuf Saeed Hajj Ali on September 5, 1990, but that his father changed his name that year to Abdulazeez.

U.S. law enforcement officials said he was a naturalized U.S. citizen.

His former coach in mixed martial arts, Scott Schraeder, thought of him as "all-American."

"There were tears in my eyes," Schraeder said of the moment he heard the news. "He was one of the nicest kids we trained."

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Next to his senior yearbook photo from 2008, Abdulazeez added a quip he attributed to "Hijabman." "My name causes national security alerts. What does yours do?" it said.

Wagner said she believes he was making a joke, and never thought he could do anything like what happened in Chattanooga.

"It was funny at the time," she said, "and now, it's a little morbidly ironic."

The two classmates lost touch after graduation. Abdulazeez went to the University of Tennessee at Chattanooga, where he graduated with a degree in electrical engineering in 2012.

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Called in sick at work

Abdulazeez previously worked as an engineer with FirstEnergy nuclear power plant in Perry, Ohio, but was dismissed after 10 days in 2013.

According to FirstEnergy spokesperson Todd Schneider, it was determined that Abdulazeez did not meet minimum requirements for ongoing employment.

His employment with the plant was first reported by the Associated Press.

Abdulazeez most recently worked at the Franklin, Tennessee, location of wire and cable manufacturing firm Superior Essex Inc., the company confirmed in a letter distributed to employees.

He had worked there for three months, the company said, without offering any details about what he did or how he performed.

CNN affiliate WKRN-TV , citing an unnamed Superior Essex employee, reported Abdulazeez had called in sick Monday and Tuesday and was scheduled to be off Wednesday and Thursday.

People who knew Abdulazeez described him as religious.

"He was a devout Muslim and used to talk about his families' prayer habits, and that always interested me to hear about his culture," said Samantha Barnette, another former classmate.

He at times interrupted training sessions with fighting coach Schraeder to pray.

"I wouldn't call it overly religious," Schraeder said. "He followed his religion; he would pray at 6 o'clock. He'd go into our office and pray." But he would skip prayers at times, he said.

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Return to Middle East

Abdulazeez also once trained as a fighter under coach Almir Dizdarevic. They knew each other from mosques they attended, even after the training relationship ended. They would bump into each other and chat, or Dizdarevic would speak with his family.

He had heard his former athlete moved to the Middle East a year or so ago.

"He went back home and he stayed overseas," Dizdarevic said. "And I asked his dad about, you know, where's Mohammad? I haven't seen him in a while, and he said, 'He moved back home.'"

Jordanian authorities say an individual with the same name as Abdulazeez traveled in and out of Jordan several times over the years. However, the traveler used a U.S. passport, not a Jordanian one, Jordanian government officials told CNN.

Jordanian officials are struggling to gather information because, "the name is very vague. It is a three-part name, so we are facing difficulty in getting to the bottom of it," one government source said. Investigators in Jordan are working closely with U.S. authorities to match the three-part name to people born in 1990, government officials added.

Radicalized?

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Dizdarevic can't believe Abdulazeez was radicalized through anyone in Chattanooga. Any extremism influence would have had to come from somewhere else, he said.

Investigators have not mentioned finding any social media activity by Abdulazeez -- unusual for a man in his 20s. Investigators are examining a blog authored by a user designated as "myabdulazeez," but they have not confirmed that it belonged to the gunman.

Only two posts appear on it, both dated three days before the shooting. One compares life on Earth with being in a pleasant prison. The other encourages readers to follow historic Islamic figures, who the writer said fought in jihadi wars.

Not in databases

Abdulazeez was not in any U.S. databases of suspected terrorists, a U.S. official said.

His only reported prior trouble with the law was a DUI arrest in April. His court hearing was scheduled for July 30.

A police officer stopped Abdulazeez for failing to maintain his lane, driving slowly and stopping at green lights. According to a police affidavit, the officer "noticed an odor commonly associated with an alcoholic beverage and the odor of burnt marijuana" coming from Abdulazeez.

He was unsteady, with droopy eyelids and slurred speech, and had a white powdery residue under his nose, police wrote, adding that Abdulazeez said the white substance was crushed caffeine pills.