U.S. President Barack Obama talks to the media in the Oval Office in Washington about shootings at military facilities in Chattanooga, Tennessee, July 16, 2015. Reuters/Yuri Gripas

President Barack Obama sent out his “deepest condolences” to victims’ families Thursday following an attack at two military sites in Chattanooga, Tennessee. A gunman opened fire on a Navy and Marine reserve center, leaving four Marines dead, and wounding several others, officials said.

"I speak for the American people in expressing our deepest condolences" to victims of the Chattanooga rampage, Obama said Thursday to reporters in the Oval Office. “I ask all Americans to pray for the families that are grief stricken.”

The suspected shooter, 24-year-old Mohammod Youssuf Abdulazeez, was shot dead, the FBI said. The rampage reportedly began around 10:45 a.m. EDT at a military recruiting center in a Chattanooga strip mall. It ended about 30 minutes later at the reserve center on Amnicola Highway. Authorities said at least one local police officer was reportedly wounded in an exchange of gunfire with the shooter.

The president said he was briefed about the shootings and has been in touch with the Defense Department to make sure military facilities are on alert.

"My main message right now is obviously the deepest sympathies of the American people to the four Marines that have been killed," Obama said. "It is a heartbreaking circumstance for these individuals ... to be killed in this fashion."

Obama also said the FBI is leading the investigation into the shootings.

“We haven't determined whether it was an act of terrorism or a criminal act,” he said. Authorities are investigating “every possible avenue,” Ed Reinhold, FBI special agent in charge, told reporters Thursday.