President Obama late Wednesday received updates on the shooting at Ford Hood, Texas, and said he was “heartbroken” over the second episode of mass violence at the military base in recent years.

“We’re heartbroken that something like this might have happened again,” the president said while in Chicago for fundraisers.

“Just for now, I would hope that everyone across the country keeps the families of Fort Hood in our thoughts and our prayers,” Obama added. “The folks there have sacrificed so much on behalf of our freedom.”

Fort Hood is on lockdown in the wake of a shooting that killed at least four people, according to media reports. The military installation also acknowledged a report that the shooter was killed but said that information was not confirmed.

The base was the site of a mass killing just five years ago that left 13 dead and more than 30 wounded in the most deadly shooting at a military installation in American history.

Obama pledged Wednesday that his administration would get to the bottom of what happened.

“Any shooting is troubling,” Obama said. “Obviously this reopened pain of what happened at Fort Hood five years ago. We know these families. We know the service to their country and the sacrifices that they make.”

The president added that his national security team was in contact with both the Defense Department and the FBI.

“We don’t yet know what happened tonight but obviously that sense of safety has been broken once again,” Obama said. “We need to find out exactly what happened."

This story was first published at 8:48 p.m. on April 2 and was updated at 8:54 a.m. on April 3.