The FBI said Wednesday that it was treating the gunman in the Chattanooga, Tennessee, killing of five service members as a "homegrown violent extremist" and that it was still too early in the investigation to see if he had been radicalized. Ed Reinhold, the FBI's special agent in charge in Knoxville, said that officials were still conducting an investigation of Mohammod Youssuf Abdulazeez, the gunman who was killed by police after the July 16 shootings, according to the Associated Press.

Reinhold also said that authorities believed Abdulazeez, 24, acted alone in Thursday's shooting of two military sites that killed four Marines and a Navy sailor. Officials provided details about how the incident played out. A military official said at the news conference that a number of service members rushed back "into the fight" after taking others to safety during the shooting.

Maj. Gen. Paul W. Brier, commanding general of the 4th Marine Division, said the troops "reacted the way you would expect," during such a situation, moving from room to room to help others.

Five guns were recovered at the site of the shooting, three of which belonged to Abdulazeez and two to service members, according to the FBI. Reinhold said during the news conference that at least one service member fired at Abdulazeez. He also said, after being asked about friendly fire, that preliminary reports indicated that all five service members were killed by the same gun.

Reinhold provided a detailed description of how the shooting reportedly happened. He stated that a service member fired at Abdulazeez after he crashed his rented, silver Ford Mustang through the gates of the facility. Abdulazeez then entered the building, shot a service member, went throughout the facility and made his way outside killing two more people before the shootout with Chattanooga police, according to Reinhold.

Abdulazeez had reportedly struggled with drugs, alcohol and depression. He also expressed suicidal thoughts and wrote about "becoming a martyr" in 2013 after losing his job, according to ABC News. Reuters reported Tuesday that investigators had evidence Abdulazeez searched for general jihadist propaganda online but there was not yet any direct link to a specific group. Abdulazeez told his friend James Petty that ISIS was "doing wrong," and called it a "stupid group" whose actions were "completely against Islam," according to a CNN interview Monday.