Four U.S. Marines were killed after a lone gunman went on a shooting spree in "an act of domestic terrorism" in Chattanooga, Tenn., the Pentagon confirmed Thursday.

The Federal Bureau of Investigation identified 24-year-old Muhammed Youssuf Abdulazeez as the shooter. He was killed by law enforcement at the second of two locations where Abdulazeez attacked.

In an Oval Office speech, President Obama offered his condolences to the Marine Corps families and said he has been in contact with the Pentagon to ensure appropriate measures are in place "to ensure all our defense facilities are properly attentive and vigilant."

For the last several weeks, the Islamic State has called for attackers to strike U.S. facilities such as military bases during the annual Ramadan celebration, which ends Friday.

"My main message right now is [to share] 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 who have served their country with great valor."

He asked for the nation's prayers as authorities were in the process of notifying the victims families.

Based on a timeline provided by the Pentagon, Abdulazeez arrived at a military recruiting center in a Chattanooga strip mall around 10:45 a.m. and shot 25-30 rounds through the center's glass door from his automobile, never leaving the car or stepping into the recruiting center. The center was full of recruits and recruiters who were able to escape through the back.

Abdulazeez then led responding police through a chase to the second location a Navy Reserve Center, arriving around 11:30 a.m. Before Abdulazeez was killed, he was able to shoot and kill four U.S. Marines.

Federal law enforcement agencies immediately took the lead on the investigation, with U.S. attorney Bill Killian calling the attacks "an act of domestic terrorism."

"Because families not been notified, I am not going to release any of the particulars about the victims at this point," he said. The military has a standard practice of not identifying victims until 72 hours after it has notified the victim's family.

Press reports indicated that two others besides the Marine shot in the leg were injured, including a police officer who responded to initial 9-11 calls.

By Thursday afternoon, the U.S. Marine Corps confirmed the four fatalities, but said their names would only be released after their families have been notified.

"We can also confirm one Marine Corps recruiter sustained a wound to the leg while working at the Chattanooga recruiting office," said Maj. Paul L. Greenberg. "The recruiter was treated at a local hospital and has been released."

"Today's cowardly attack is a reminder that our men and women in uniform are under constant threat, no matter where they serve," said House Speaker John Boehner, R-Ohio. "I'm deeply saddened by this loss of life, and on behalf of the whole House, offer condolences to the families who lost loved ones today. Our thoughts and prayers are with them, the people of Tennessee, and all of our troops."

The Council on American-Islamic Relations also condemned the "horrific" attack.

"The American Muslim community stands shoulder to shoulder with our fellow citizens in offering condolences to the loved ones of those killed and injured and in rejecting anyone who would harm our nation's safety and security," the group said. "Our thoughts and prayers are with the families impacted by this tragedy."