The fire fighter that died has been identified as 48-year-old Lt. Vincent Perez. A second male firefighter, identified as Anthony Valerio, 53, is in critical condition and the third firefighter, a female, is in fair condition and has been released from the hospital.
The cause of the fire is still being investigated but what is known is that the firefighters inside the home reported experiencing a "flash" as they battled the blaze in which everything inside the home that was combustible suddenly ignited at once. It is considered one of the most dangerous situations firefighters can face.
"It's kind of a mixture of heated gases and oxygen and the fuel and it all reaches a certain ignition point and it all ignited at one time," San Francisco Fire Department spokesperson Mindy Talmadge said.
Neighbors say the situation unfolded quickly.
"I came outside to walk my dogs and I saw three girls run out of the house and there was just a little bit of smoke coming out of the garage and I said, 'What's going on?' and they said, 'We're calling 911, there's a fire,'" Patty Stanton said.
"I saw the firemen outside the front of my house gearing up and I didn't see much smoke and then a few minutes later there was just tons of black smoke billowing out," Kay Young said. "I was actually thinking I maybe needed to leave my house."
The fire began at 10:45 a.m. on the 100 block of Berkeley Way. The four people living inside the home escaped without injury. The four-story home sits on a hillside facing Glen Canyon, making it difficult for firefighters to battle the flames.
Once the firefighters inside the home experienced the flash, an emergency signal was triggered and after fire dispatchers received no response from the firefighters, a rescue crew was sent into the home to rescue them.
"They went in and did their operations and at some point two of our members were found down on the ground and they were pulled out and transported to the hospital," Talmadge said.
Firefighters gathered at San Francisco General Hospital Thursday afternoon to mourn the loss of one of their own. Perez's body was taken away from the hosptial with escorts from the fire department. Fire Chief Joanne Hayes-White called him valiant as she made the painful announcement about the loss of one of their own.
"We have been able to notify his family and I did want to ask you to keep his family and the San Francisco Fire Department family in your thoughts and prayers for the line of duty death of Lt. Vincent Perez," she said. "Vince was a great guy; he served valiantly in the San Francisco Fire Department for 21 years."
Both of Perez's brothers are police officers, one in San Francisco and the other in Oakland.
San Francisco Mayor Ed Lee released a statement Thursday afternoon saying, "I am deeply saddened by the tragic death of a SFFD firefighter who died today in the line of duty. This is a devastating day for our City, and I join all of San Francisco in expressing our deepest gratitude and profound sorrow for the loss one of our own." Lee has ordered that flags to be flown at half-staff at all city buildings in Perez's honor.
Valerio is still being treated at San Francisco General Hospital and is in critical condition. A vigil was set up outside with firefighters and other city officials.
"He drew in hot air and smoke and they don't know how long he was in the smoke, so he has a lot of stuff coming out of his body," said Mark Valerio, Anthony's brother.
The last San Francisco firefighter killed in the line of duty was Melinda Oller, who fell off a fire truck while responding to an emergency in 2003. The last one killed in a fire was in 1995 when Louis Mambretti became trapped in a burning Diamond Heights garage in a fire fueled by 70 mile an hour winds less than a mile from Thursday's incident.