One person leapt from a second-floor window of a burning townhouse in Northwest Washington Thursday, and three others were rescued by D.C. firefighters.

About 6 p.m., firefighters found heavy fire pouring from windows on the top floors of the building at the Sursum Corda complex on K Street, just west of North Capitol Street, said Battalion Chief Donald Martin. The complex is about a mile north of the U.S. Capitol.

The man who jumped from the second-floor window was taken to a hospital with potentially life-threating injuries, Martin said. Two of the three people who were rescued from the third floor of the building were taken to hospitals with smoke inhalation injuries, but their injuries appeared to be less severe. And a firefighter was treated for an injured hand.

Firefighters knocked down the bulk of the fire in about 15 minutes.

“I’m extremely proud of our members’ work and efforts,”department Chief Brian Ellerbee said at the scene of the blaze.

The cause of the fire is under investigation.