Jose Tienda didn't know the workout class he was coaching would lead to a life-saving workout of his own.

He had clients performing running exercises outside his Crossfit Dark Element gym on North El Dorado Street when he noticed flames and white smoke coming out of the roof of the Mayfair Apartment building across the street.

"I didn't see any fire department or anybody like going around the area so I knew I had to take action at that time. I ran inside looking for a fire alarm or people moving. So, nobody was really moving so I knew these people were still asleep. I started pounding on the doors and finally got to the third level and I noticed a guy had smoke coming out of his room. I pounded on the door and he came out. He had a big gash on his head," said Tienda.

Tienda says the man told him something exploded while he was cooking. Tienda then brought him downstairs outside to the curb, pulled the building fire alarm and continued knocking on doors.

He says many residents who answered doors appeared to be just waking up.

The Stockton Fire Department confirms one resident was taken to the hospital for treatment. The resident was treated for a gash to his forehead and released.

46 units are in the building. It's unknown exactly how many people were living inside when they were evacuated.

The exact cause is not known.

"There's dangers to that obviously entering a building without protective gear and going up and trying to get people out, but it's a good thing we have people willing to take that risk," says Brandon Doolan, Battalion Chief with the Stockton Fire Department.