Investigators are trying to determine the motive of the 24-year-old gunman who opened fire at two military offices in Chattanooga, Tenn. on Thursday; killing four Marines in what authorities believe could be an act of terrorism.
Mohammad Youssuf Abdulazeez, identified as the shooter by the FBI, was also killed in the shooting. He was a naturalized American who was born in Kuwait. U.S. law enforcement authorities said they were investigating whether the shooting rampage was a terrorist attack inspired by a militant group like ISIS, according to Reuters.
Authorities "have not determined whether it was an act of terrorism or whether it was a criminal act," said Ed Reinhold, FBI special agent in charge. "We are looking at every possible avenue, whether it was terrorism - whether it was domestic, international - or whether it was a simple, criminal act," he said, according to CNN.
Islamic State had threatened increased attacks during the holy month of Ramadan, which ends on Friday evening. The SITE Intelligence Group, which monitors terrorist organizations, said that Abdulazeez wrote on his blog on Monday that "life is short and bitter" and Muslims should not miss the opportunity to "submit to Allah."
Even though Abdulazeez was not previously under the surveillance of counter-terrorism agencies, federal officials familiar with the inquiry said that his father was investigated years ago for having possible ties to a terrorist group, according to New York Times.
