Shootings at a pair of military facilities in Chattanooga, Tenn., Thursday, left five people dead, including four Marines and the lone gunman, officials said.

The shooter was later identified by the FBI as 24-year-old Mohammod Youssuf Abdulazeez, and it was revealed late Thursday by SITE, a widely read website that tracks Islamic terrorism, that he maintained a blog where he wrote “Islamic-focused” posts that were entered as recently as three days ago.

An FBI official told Yahoo News, "there is no reason to question the authenticity" of the blog with the pro-jihad entries. The official said it is actively investigating whether the shooter may have contacts with ISIS through social media, but currently has no evidence of that.

In a July 13 post, Abdulazeez wrote that “life is short and bitter” and that Muslims should not let “the oppourtunity to submit to Allah…pass you by,” the website said in an email sent to subscribers.

He also stressed the sacrifice of the Sahaba [companions of the Prophet] with mention that, "Every one of them fought Jihad for the sake of Allah. Every one of them had to make sacrifices in their lives and some even left all their wealth to make hijrah to Medina,” he wrote, according to SITE.

A U.S. official told the Associated Press that Abdulazeez had not been on the radar of federal law enforecment before Thursday's shooting. His father had been investigated several years ago for "possible ties to a foreign terrorist organization" and added to the U.S. terrorist watch list, according to a report in the New York Times, but that probe did not surface information about Abdulazeez, the paper said.

Late Thursday night in a Chattanooga press conference, FBI officials maintained that there is no threat to the general public following the shooting, which left local officials and residents reeling.

"It is incomprehensible to see what happened," Mayor Andy Berke said at a news conference Thursday afternoon. "This is a nightmare for the city of Chattanooga."

Three other people, including a Chattanooga police officer, were wounded in the shootings, Berke said. They were transported to local hospitals with non-life-threatening injuries.

The shootings began shortly after 10:30 a.m. at a National Guard office in a strip mall on Lee Highway, where the suspect fired from his car, aid the FBI. A witness there described hearing as many as 20 shots fired there before the gunman fled. A photo posted to Facebook by a witness shows the door of the office littered with bullet holes.

(Courtesy of April Grimmett/Facebook) More

Police say Abdulazeez then drove to the Chattanooga naval reserve center, where a witness told CNN she saw a man with "a high-powered rifle" fire multiple shots from a convertible silver Mustang into recruiting offices at the center shortly before 11 a.m. ET.

Four U.S. Marines were killed at the naval center. Their names have yet to be released.

Abdulazeez was killed at the scene. Ed Reinhold, special agent in charge of the FBI's Knoxville field office, said late Thursday night that Abdulazeez got out of his car before killing the Marines.

"Somebody brutally and brazenly attacked members of our armed forces," Chattanooga Police Chief Fred Fletcher said at the afternoon news conference.

Because the shootings occurred at U.S. military facilities, the FBI is leading the investigation.