Chattanooga gunman spent time in Middle East

The 24-year-old gunman who on Thursday killed four U.S. Marines in a shooting spree at two military facilities in Chattanooga, the U.S. state of Tennessee, was in the Middle East last year for about seven months, media reports said on Friday.

U.S. law enforcement and intelligence officials are still scrambling to piece together information of the suspected shooter, who they acknowledged earlier was not on their terrorist watch list.

According to a report by The New York Times, U.S. officials familiar with the shooting incident said that Muhammad Youssef Abdulazeez, a naturalized U.S. citizen originally from Kuwait, spent about seven months in Jordan in 2014, and authorities were currently examining personal belongings and media contacts of Abdulazeez to see whether he was in touch with any extremist groups during his sojourn in Jordan.

The Washington Post earlier quoted senior officials from the Federal Bureau of Investigation (FBI) as saying that the shootings did not appear to be related to any terrorist group. However, the FBI said on Thursday that it would treat Thursday's shootings as a terrorism investigation until it could determine it was not.

The Thursday attack left four U.S. marines dead and three others wounded, while the gunman was also killed by the police.

According to local police, the two shootings, which lasted about 30 minutes, happened around 11 a.m. local time at a military recruiting center and the Naval Reserve Center about 10 kilometers apart. The shooter reportedly fired shots while driving in an open- top Mustang.

The shooting incident came at a time when U.S. authorities were increasingly concerned about terror threats posed by domestic sympathizers of the Islamic State extremist group, which had earlier called on its supporters to carry out lone-wolf attacks against its enemies worldwide.

The U.S. military in May announced that security status at domestic military bases was raised to "Force Protection Bravo," a level defined as an "increased and predictable threat of terrorism. "

In the wake of the Chattanooga shooting, the U.S. Defense Department said on Friday that the general security level has not been raised at military installations around the country. However, it advised individual station commanders to take extra precautions at their discretion.