Authorities have identified the gunman who killed four marines in Chattanooga, TN, as Muhammad Youssef Abdulazeez, according to CBS News.

Abdulazeez, who also wounded a police officer and a soldier, died during the attack on two military facilities.

According to the Associated Press, Abdulazeez was a naturalized citizen who was originally from Kuwait. At the time of the shooting, he was a resident of Hixson, Tennessee, and was arrested earlier this year for driving under the influence. Aside from the DUI, authorities do not believe he has a criminal record, and his name has not yet been spotted in any government intelligence databases.

While a motive for the attack has not been released, Twitter accounts associated with ISIS have allegedly claimed responsibility, with some sites claiming the tweets preceded or corresponded with the start of the attack.

However, the timing and authenticity of the tweets has not yet been verified. And while this is likely an act of terrorism, authorities are still exploring all avenues. As CNN reports:

Investigators “have not determined whether it was an act of terrorism or whether it was a criminal act,” Ed Reinhold, FBI special agent in charge, told reporters. “We are looking at every possible avenue, whether it was terrorism – whether it was domestic, international – or whether it was a simple, criminal act.”

(Source: CBS News, H/T: Heavy.com)