(TNS) — Firefighters in western Pennsylvania had to not only deal with a house on fire but the 20,000 rounds of ammunition inside that started igniting around them.

A home in Vandergrift, Westmoreland County, caught fire at around 8 a.m. Friday when a neighbor saw smoke pouring from the roof, reported KDKA-TV in Pittsburgh.

That neighbor tried to warn the homeowner but she was not there and showed up a little while later.

Arriving firefighter crews were quickly pulled out of the home when ammunition began going off.

“It was constant pops,” a neighbor told the station. “It was very scary because nobody knew where (the shots) were going.”

Vandergrift Fire Chief Randy Dunmire told KDKA that he pulled his crews as soon as shots rang out.

“It’s just kind of flying around some,” he said. “It doesn’t have a lot of velocity to it because it’s not coming out of a barrel, but it still has enough from the powder.”

Firefighters stayed outside battling the fire for about 30 minutes after the shots stopped.

“We decided if we didn’t hear any for 10 minutes, then it was OK to go in,” the fire chief said.

Some shell casings were found a half a block away, KDKA reported.

Dunmire said crews retrieved rifles and handguns from the home but several more were destroyed. He said the state fire marshal is investigating, but he thought the blaze was accidental.