The Chattanooga, Tennessee, shooter, 24-year-old Mohammod Youssuf Abdulazeez , reportedly failed a background check at a nuclear power plant in Ohio in May 2013, the Associated Press reported. An Ohio company, FirstEnergy Corp., broke the news but did not specify why Abdulazeez did not pass the screening process.

Four Marines died when Abdulazeez opened fire Thursday morning at two military facilities in Chattanooga. Abdulazeez died in the second shooting. Department of Justice officials said at a news conference Friday that the motive of the attack is still unknown.

Todd Schneider, a spokesman for FirstEnergy Corp., says Abdulazeez was conditionally hired as an engineer at a nuclear plant in East Cleveland. He spent 10 days there before he was let go because he failed a background check, according to the AP. FirstEnergy provides electricity to several states, including Pennsylvania and West Virginia.

Despite his failing the background check, FBI officials said there is no evidence suggesting Abdulazeez should have been monitored as a terrorist threat.

“Abdulazeez was not in any U.S. databases of suspected terrorists," a U.S. official said, CNN reported. “His only reported prior trouble with the law was a DUI arrest in April. His court hearing was scheduled for July 30.”

The FBI said that Abdulazeez was armed with at least two rifles or shotguns, as well as a handgun, when he opened fire Thursday, the Washington Post reported.

FBI officials said Abdulazeez was a naturalized U.S. citizen, a Kuwaiti-born Jordanian, and attended a regional high school near the scenes of the shootings, a Marine recruitment office in a strip mall and a Marine training facility.

Abdulazeez allegedly had a blog that appeared to illustrate his hard-line religious beliefs, the Daily Beast reported. The blog had only two posts, both published July 13.

Abdulazeez also took several trips to Jordan, a Muslim-majority country considered one of the more stable Middle Eastern nations, Reuters reported. U.S. authorities are still trying to determine if Abdulazeez came into contact with any radical terrorist groups or extremists during his travels.

Jordan is one of the main crossings for foreign fighters wanting to enter Syria. It is also a host country for hundreds of thousands of Syrian refugees. According to the Post's report, about 2 million people travel from Jordan to the U.S. every year.