ROXBOROUGH, Colo. -- Fire investigators were set to return Monday to the scene of an explosion and fire that killed three people and critically injured a fourth in Roxborough early Sunday.

Neighbors said the people were gathered at the home to console the grown son of a woman who died of brain cancer on Saturday. The son died in the fire.

Although official identification of the dead has not been released, friends and neighbors identified the son as Joey Shedron, 23. Also dying in the fire was his girlfriend, Amber Jeffers, 18, and a friend, Jeremy McCarroll, 20.

The man who was critically injured in the fire had burns over 70 percent of his body, including his face, arms and head. He was undergoing treatment at University Hospital's burn center Monday and has not been identified. A fourth man escaped the explosion and blaze unharmed.

As many as 18 people were in the home earlier as news spread of the death of Joey Shedron's mother.

The explosion and fire was reported shortly after 3 a.m. at 9877 Fairwood St. in the Roxborough subdivision in the southwest section of the metro area.

Stuart Buckley, 37, lives across the street and saw the fire. He dialed 911 then went outside where he found the injured man a few houses down, his hair burned off, burns on his legs, torso and arms and still smoldering.

"His belt was still on fire or glowing from it," said Buckley, still shaken from the experience hours after. Unable to render aid because of the severity of the injuries, he comforted the man until paramedics arrived.

The house was reduced to smoldering ruins, a few hardy studs ringing its concrete foundation like crooked, blackened matchsticks.

Firefighters had to wait more than six hours for the remains to cool before they could begin their search of the rubble. Wearing air tanks and protective clothing, firefighters slowly combed the house from one corner to the other.

"There's nothing left of the house," Matthews said. "They're standing in a pile of rubble."

Buckley and other neighbors calling 911 reported booms and loud popping sounds, and said the house exploded but Matthews said firefighters have been unable to determine what happened.

Steve Lesser, 45, who lives a couple of houses down looked out his window, saw the fireball and thought it was too early for the sun to be coming out before he realizing his neighbor's house was burning.

Buckley said he earlier had stopped by the house for a beer at a small gathering of about a dozen people. He said the atmosphere at the house, which was occupied by a father and son, usually resembled a frat house, with people coming and going.

"If I had stayed there I would have been dead," he said.

Families of those missing were notified and had made their way to the scene before firefighters discovered the bodies.

Neighbor's said Joey Shedron's father owns a motorcycle shop and motorcycles were kept in the attached garage, where they were repaired and worked on.

Hundreds of people attended a vigil for the victims Sunday night, where Pastor David Jarboe said residents moved to the area to be part of a smaller community and get to know each other.

"We've got to do something," he said. "We've got to gather as a community."

Amateur video from Brandon Sharpe. More video can be seen here.