CHATTANOOGA, TENNESSEE (TIP): Four Marines were killed during what’s being called a “brutal and brazen attack” at a Naval recruiting station Thursday, July 16 morning in Chattanooga.

A Chattanooga police officer responding to the shooting was shot in the ankle and is in stable condition at Erlanger Medical Center. He was identified as veteran officer Dennis Pedigo. His family is reportedly with him at the hospital.

NBC News quoted a defense official as saying a Navy sailor was also shot multiple times and was “critically injured.”

The shooter was also killed, though authorities will not say how he died. A Senior Federal Official confirmed to NBC NEWS that the suspect was Muhammad Youssef Abdulazeez, a naturalized U.S. citizen from Kuwait. He is from Hixson, which is just a few miles across the river from Chattanooga.

The suspected gunman, Mohammad Youssuf Abdulazeez, first opened fire at a military recruitment office, located in a strip mall off Lee Highway in Chattanooga. Witnesses saw Abdulazeez spray a hail of bullets at the glass doors of a military recruiting center in a strip mall .Then the gunman, who according to a law enforcement official was driving in a rented silver Ford Mustang convertible, moved on to his next target more than seven miles away: a Naval reserve center. There, he rammed into a gate at some point during his shooting rampage and was eventually killed by police, a U.S. official said.

The shooting resulted in the death of four Marines.

Mohammad Youssuf Abdulazeez was carrying 30-round magazines when he opened fire, according to a source briefed by law enforcement. Abdulazeez kept police at bay for some time with the amount of ammunition he had, according to the source.

The shooting suspect was armed with an AK-47 style weapon‎ at the time of the attack according to two law enforcement officials briefed on the investigation.

Suspected shooter Mohammad Youssuf Abdulazeez, 24, is dead, the FBI said. But — publicly, at least — investigators haven’t said much more about him.

Now, with the FBI in the lead, a terrorism task force is investigating, a law enforcement source said.

Authorities “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.”

A key detail will help them make that determination: finding out the suspect’s motive.