DORCHESTER — Boston firefighter Robert T. "Bobby" Kilduff Jr. had spent 24 years going into burning homes. Three generations of his family had done the same job. Late Saturday night, he climbed to the third floor of a burning wood-frame house on Treadway Road. Just after 9 p.m., he fell.

Here is how the night went down.

Boston Fire was called to 18 Treadway Road — off Savin Hill Avenue, near Dorchester Avenue — at about 8:15 p.m. on Saturday. Within twelve minutes the call had been upgraded to a 3-alarm. Heavy fire was already showing.

Companies attacked from both inside and outside the structure. The home was burning on all three floors. Rescue 2 — the squad Kilduff was assigned to — was working the building.

Multiple ladders went up. Ground crews worked below, aerial crews above.

The fire burned through the roof. Crews held it to 18 Treadway, stopping it from spreading to the homes pressed against either side. From the street, Boston Fire's own photos showed the flames erupting from the third-floor peak.

Somewhere in that fight, Kilduff fell.

Boston EMS packaged him for transport. Boston Police set up a safety corridor. The ambulance ran lights and sirens to Boston Medical Center.

He was pronounced there.

Around 1 a.m. Sunday, a dignified transfer left BMC, escorted by police. Photos circulated through the Boston firefighter community within minutes.

Kilduff was a third-generation Boston firefighter. His grandfather and father wore the uniform before him. He served in the United States Marine Corps before joining the Boston Fire Department 24 years ago. He was assigned to Rescue 2.

This is a developing story.