"I just heard this big boom," Lisa Armijo, a neighbor who lives next door to the school, said.
Construction workers were doing work inside the middle school gymnasium. No students were inside because school is not in session.
"I turned the corner and saw smoke coming out of the building, and then I saw workers running in," Armijo said.
Armijo saw the three injured men come out.
"I saw one coming out just wearing shorts and no shirt and socks on," Armijo said. "I heard there was one behind the school that was burned on his arm, and then we saw the other come out of the building and into the helicopter."
Investigators say all three were hurt either by falling or from burns to their bodies.
"I feel really sad and hope they're okay," Armijo said. "I'm praying for them."
"If it's any of the guys I know it's really sad. I hope it's none of them," Ozzie Mutz, a neighbor who lives across from the school, said.
Investigators aren't sure if the men were on the roof or injured from the collapse. They say the explosion did happen inside the gym.
"I'm just glad there were no kids in there," Armijo said.
"It's really sad," Mutz said. "Our thoughts go out to the victims and the people who got hurt and their families."
No homes around the school had to be evacuated.
The Vice President of the company doing construction at the school says the three guys who were injured were sub-contractors of his company. He's been told they are all in stable condition.
(KUSA-TV © 2012 Multimedia Holdings Corporation)