AURORA, Colo. (CBS4) – A spark from a welder sparked a fire that broke out around 10:30 a.m. Saturday in the 4600 block of South Norfolk Way.

Investigators say they found thousands of rounds of ammo in the garage and basement. Shell casings were even lying in the street.

“We heard an explosion and it sounded like firecrackers going off. Our kids came in the house and said the neighbor’s house is on fire,” John Childs said.

Childs took house sitting to a whole other level. He took cellphone video shortly after a neighbor’s house burst into flames.

Childs and other neighbors can be seen in the video grabbing a hose to battle the blaze.

“And realized there was no putting it out,” Childs said. “So I got the guy across the street, tended to his wounds and made sure there was nobody in the houses next door.”

The homeowner was rushed to the hospital for burns. Flames still flared up about an hour after the fire sparked in the garage.

“The investigators are aware of other ammunition, and they are being cautious,” Cpt. Diane Lord with the Aurora Fire Department said.

Investigators believe thousands of rounds of ammo in the home may have caused the explosion neighbors heard.

“There’s always a potential when there’s explosives and fire to be more dangerous. Fortunately the crews did a good job of putting out the fire quickly,” Lord said.

As crews put out hot spots, Childs is glad he was in the right place at the right time.

“I just hope the guy is okay. Like I said, he was burned pretty good, and that’s all he was asking for was help,” Childs said.

There’s no word on the extent of the homeowner’s injuries. Lord says no one else was home at the time and no other houses were damaged.