Ed Smith bolted out of his house in Delmont when he heard a loud explosion, followed shortly by a second blast on Thursday afternoon.

“I found a gentleman (lying) in the snow outside the garage with no clothes. Half his clothes were burnt,” Smith said. “The second explosion blew the window right out of the house.”

The man was flown by medical helicopter to West Penn Hospital in Pittsburgh following the apparent explosion at a Spring Lane apartment building around 3:20 p.m., according to the Mutual Aid Ambulance Service.

Smith said the victim repeatedly mentioned a propane heater he had been using to heat the apartment.

Delmont fire Chief Don Cline suspects the victim was carrying one of the heaters outside when it exploded.

“Nobody should have any propane stuff inside their homes,” he said.

The blast caused significant damage to the low-rise building. A garage door was buckled, and the main window facing Spring Lane was blown out, lying on the ground as fire crews investigated. Multiple fire companies remained on the scene throughout the afternoon.

“It was loud,” said a neighbor who declined to give his name. “Honestly, I thought someone hit my car.”

“We never had anything like this happen before,” Smith said. “The police and fire department were here very quickly, but it took the (Mutual Aid) ambulance almost 15 minutes to get here, and they’re right here in Delmont.”

Mutual Aid spokesman Shawn Penzera said an ambulance arrived on Spring Lane in less than 15 minutes.

“A lot of times, in emergency situations, it feels like things take a lot longer than they actually do,” Penzera said.

Authorities closed Spring Lane and adjacent Highland Street while a state police fire marshal worked to determine the cause of the blast.

No foul play is suspected, said Delmont police Chief TJ Klobucar.

“I heard from multiple people how quick the response was from our police department, the neighbors, along with the fire department,” he said.

White Valley, Forbes Road, Export, Sardis and Claridge volunteer fire departments also responded to the scene, Cline said. The victim’s two pet rats, who survived the explosion, are being treated by the Westmoreland County Animal Response Team.