Chattanooga Shooting
Members of the FBI Evidence Response Team investigate the shooting at the Armed Forces Career Center/National Guard Recruitment Office in Chattanooga, Tennessee, on July 17, 2015. Joe Raedle/Getty Images

Federal authorities have opened an ongoing "terrorism investigation" into the fatal shooting Thursday of four U.S. Marines at military facilities in Chattanooga, Tennessee, officials confirmed Friday. Law enforcement representatives said Mohammod Youssuf Abdulazeez, the 24-year-old man identified as the Chattanooga shooter, carried at least three firearms and a vest full of ammunition when he was killed in a shootout with police.

"We will continue to investigate this as a terror attack until facts lead us otherwise," U.S. Attorney Bill Killian said, according to WTVC in Chattanooga. "We will leave no stone unturned for the victims of this heinous act."

Federal officials have followed up on about 70 leads since Thursday as part of their investigation into the shooting, FBI Special Agent in Charge Ed Reinhold said during a press conference. Reinhold declined to provide information on Abdulazeez's potential motive in carrying out the attack and said it would be "premature to speculate."

Abdulazeez carried at least two "long guns" and one handgun during the attack, one or more of which may have been illegally purchased, Reinhold added. The FBI has explored evidence Abdulazeez traveled to the Middle East in 2014 and will continue to assess his potential activity on the Internet and social media platforms. There was no indication that Abdulazeez had any link to the Islamic State group, also known as ISIS or ISIL. No member of his family has been arrested, though authorities did handcuff some family members during a search of his home.

Both federal and local officials praised Chattanooga police for their bravery in confronting Abdulazeez, who was killed at the scene of the attack. "The responding officers were under a tremendous amount of gunfire from the suspect," Reinhold said, according to WJLA-TV in Washington, D.C. "All the officers involved in this incident are doing very, very well. They have the support of the country," he added.