A hammer-wielding man killed a woman and her boyfriend before lighting himself on fire in a grisly double murder-suicide in Pennsylvania over the weekend, authorities said Tuesday.

Firefighters rushed to a blaze at 931 Chestnut St. in Union Township, about 50 miles outside of Philadelphia, at 5:30 p.m. on Saturday where they found Joanne Deluca, 63, and boyfriend Ira Reed, 60, slain in their living room, state police said.

In the garage, first responders found a third person, who took his own life by lighting himself on fire, officials said. That body was burned beyond recognition and it will take about three weeks for DNA tests to identify him, authorities said.

Deluca's adult son, a man in his 40s, lived with the couple, but police stopped just short of calling him the killer.

"We have not located him since the fire," Pennsylvania state police Trooper David Boehm told NBC News on Tuesday.

Police also said they don't believe there's a killer on the loose.

"We don't think the public's in any danger at all, (the crime is) confined to that property," Boehm had told reporters on Monday.

And state police Lt. Scott Brennan admitted that it's "fair to say" that investigators consider Deluca's adult son a suspect.

Police have recovered the murder weapon.

"Both died from blunt force trauma. The weapon used was a hammer," Boehm said. "Both people were killed with a hammer ... multiple blows with a hammer."

The couple's two cats and two dogs had also been violently killed, officials said.

"One of our veteran investigators said it was the worst crime scene he'd ever seen," Boehm said.