On July 16, 2015, Mohammad Youssuf Abdulazeez, 24, shot and killed four U.S. Marines and wounded three other people when he opened fire at a Chattanooga military recruiting center and attempted to continue his rampage at the Navy Operational Support Center. He was killed during a shootout with the police. Today, Abdulazeez’s motive is still unclear, but the FBI is now investigating it as terrorism.

“We will treat this as a terrorism investigation until it can be determined that it is not,” FBI Special Agent Edward Reinhold told CNN. In a press conference last night, Reinhold said, “At this point, we don’t have anything that directly ties him to an international terrorist organization.”

Abdulazeez was a naturalized U.S. citizen who worked at a wire and cable manufacturing firm in Franklin, Tennessee. He was born in Kuwait, according to that country’s Interior Ministry. While Kuwait officials said he was a citizen of Jordan, Jordanian officials say he was actually Palestinian but had Jordanian travel documents and family who lived there. Friends say he was a devout Muslim and U.S. officials say he was not included in any U.S. databases of suspected terrorists.