Robert, who didn't want to give his last name, says he was asleep when the explosion inside his own home woke him up around 2 a.m. Tuesday morning .
"It was like an earthquake is all I can say. Like an earthquake. That's all I know," said Robert, one of the victims.
A total of four men were inside the Richmond home when the explosion happened along with two dogs, Pete and Jazzy. They all survived, but the men were pretty shaken up; two of them did not want to talk about it on camera. Robert says he has no idea what could have caused the blast.
"Not sure," said Robert. "Looks like somebody threw a bomb inside the window to me. I don't know."
Firefighters were surprised by the intensity of the explosion. Investigators say the fact that the side wall of the house was blown off just shows what a tremendous blast these men survived.
"I've been with the department 16 years and this is the most significant explosion I've seen, especially with no source," said Richmond Fire Department Capt. Dane Poteet.
Firefighters first suspected a gas leak and shut the gas off as soon as they arrived. However, PG&E workers on the scene said they couldn't find any evidence of a leak. Firefighters say they also didn't see any evidence of drugs in the house. They did call in police to help with their investigation and say they haven't ruled anything out at this point.
Friends and neighbors also say they can't imagine what happened.
"I'm just glad everybody is OK and that it didn't damage the neighbors' houses," said Nancy, a friend of the victims. "That's crazy. I can't imagine what it could have been."
A total of four men were inside the home. One man was taken to the hospital and was treated for some burns to his leg, but he is fine.