Chattanooga shooting: US launches 'national security probe' after four Marines shot dead by Tennessee gunman

Officials say they are treating incident as domestic terrorism

The scene in Tennessee (AP)

The US was on a heightened state of alert and officials were investigating whether a man who attacked two military offices in Tennessee and killed four Marines may have been inspired by Isis.

It was announced that the Joint Terrorism Task Force had joined the probe into the attack as US media named the suspect as Mohammod Youssuf Abdulazeez, 24. US Attorney General Loretta Lynch said she had directed the FBI to lead the 'national security investigation' of the attack.

"The US Attorney's office and department prosecutors are also actively involved," she said in a statement.

A High School yearbook image of Mohammad Youssef Abdulazeez

Officials initially said they considered the attack to be an incident of domestic terrorism. Mr Abdulazeez, an engineering graduate, is said to be a naturalised American who was born in Kuwait.

There was no official confirmation of the suspect’s name. No-one answered the phone at his address. In a possible echo of the May attack by two men in Garland, Texas, Reuters said officials were investigating whether the Chattanooga gunman had been inspired by Isis.

"While it would be premature to speculate on the motives of the shooter at this time, we will conduct a thorough investigation of this tragedy and provide updates as they are available," the FBI said in a statement.

On Thursday afternoon, as police Swat teams raided the suspect’s home in Hixson, just a few miles across the river from Chattanooga, Jeh Johnson, head of the Department of Homeland Security, said that security at federal facilities had been raised.

The gunman, who was able to fire up to 30 shots, was killed by police officers, in the incident that began at around 10.10am on Thursday morning.

“We are treating this as an act of domestic terrorism,” said Bill Killian, the US Attorney for the Eastern District of Tennessee.

The Marines were killed when shots were fired in a Navy reserve centre in the city. The wounded Marine was hit by gunfire fired at an Armed Forces recruiting centre not far away.

President Obama said in a statement: "My main message right now is, obviously, the deepest sympathies of the American people to the four Marines that have been killed. It is a heartbreaking circumstance for these individuals who have served our country with great valour to be killed in this fashion."

“Lives have been lost from some faithful people who have been serving our country, and I think I join all Tennesseans in being both sickened and saddened by this,“ said Governor Bill Haslam.

One witness told ABC News: “It was just another regular day. He pulled up and I didn't think anything of it. He had his drop-top. He lifted a big black gun. It was one shot and then it was endless shots.”

Another witness, Erica Wright, said: “We heard a loud pop and the salon owner and I went to the window to see what was going on, we saw a silver, convertible, mustang, he was just unloading some type of large rifle.“

She added: “Initially, I saw her coming to the door, and I was telling her to go back. I just pulled off because I knew he had saw me and I didn’t want to get hit… so I pulled off and went to where people were trying to escape at the back of the building to see if she would be coming out through the back.”

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Chattanooga Police Chief Fred Fletcher told reporters the gunman acted "brutally and brazenly".

Witnesses said the gunman, driving an open-top Ford Mustang, fired at two locations about six miles. People said they heard scores of shots.