A Watertown firefighter died Friday after collapsing at the scene of a two-alarm fire. 54-year-old Joseph Toscano had been with the Watertown Fire Department for more than 20 years. He was married with five children, aged 12 to 19.

Watertown firefighters received calls for a house fire shortly after 10 a.m. Friday. The ladder truck arrived first and reported heavy fire showing.

By early afternoon investigators were surveying the scene where Joseph Toscano collapsed.

Part of the house facing the street was completely destroyed. On the second floor, it was completely burnt out and the windows were blown out.

Toscano lived in Randolph. He is the first firefighter to work for Watertown to have died after battling a fire since the late 1950s, although Boston firefighter Edward Walsh, killed three years ago battling a fire in the Back Bay along with his partner Michael Kennedy, was from Watertown.

Toscano's fellow firefighters met with stress counselors Friday afternoon. From the roof of the Watertown Fire Department headquarters, black bunting was draped over each of the bays of the fire house.

Then, Deputy Fire Chief Bob Quinn came out of the fire house. He was the incident commander at the fire.

"I arrived at approximately 10:22 and struck a second alarm immediately," Quinn said. "It was very heavy fire and smoke coming from the entire front room of the second floor of the building."

Shortly after Quinn arrived a call came that a firefighter was down.

"The firefighter was working inside the fire area, extinguishing and overhauling, when he collapsed," Quinn said.

Toscano collapsed from a medical emergency, but Quinn said he did not know the nature of the emergency.

Toscano was Quinn's aide for the past 12 years. They worked together every day. Another Watertown firefighter described Toscano as one of the best cooks in the firehouse.

EMTs took Toscano to Mount Auburn Hospital where Quinn says he succumbed to his injuries and was pronounced dead.

"We're very sad here in Watertown today to have this situation occur," Quinn said. "It's devastating to everybody behind me and everybody inside the building to have this happen."

Quinn called Toscano's death a traumatic event.

State Fire Marshal Peter J. Ostroskey says the fire is being investigated. Ostroskey says investigators believe the fire was accidental.