The Boston Fire Department is mourning the loss of a veteran firefighter killed in the line of duty.

Robert J. Kilduff Junior died while battling a house fire in Dorchester Saturday night. He fell from a third-floor window during the blaze.

Firefighter Robert Kilduff, a 24-year veteran of the Boston Fire Department, died while battling a three-alarm fire in Dorchester Saturday. (Courtesy Boston Fire Department)

Around 8:15 p.m., firefighters responded to the scene at 18 Treadway Road. The fire quickly escalated to three alarms, spreading to all three floors before firefighters knocked down the bulk of it about 20 minutes later.

The department said the firefighters were able to keep it from spreading to neighboring houses.

Around 8:50 p.m., a mayday was declared after Kilduff, of Rescue Company 2, fell from the third-floor. Boston paramedics and EMTs transported him to Boston Medical Center.

Kilduff had been a firefighter for 24 years and was a third-generation firefighter.

“Boston will always honor his life, his dedication, and his service with the deepest gratitude and respect,” Boston Mayor Michelle Wu told reporters Saturday, adding, “and we are so sorry to the family.”

Fire Commissioner Rodney Marshall said the department would work to posthumously grant Kilduff “the highest honors” firefighters can receive.

“Everyday we put on this uniform, we know in the back of our minds that something like this is a possibility, but to actually have it happen to someone you work with and actually know is something you can’t put into words,” Marshall said.

Kilduff is the first Boston firefigher to die in the line of duty since 2014.

“ Our heart goes out to the Kilduff family,” said Sam Dillon, president of the Boston Firefighters, IAFF Local 718 union, “and we ask the entire city to stand with us and stand with the Kilduffs in memory of Bobby, who laid down his life for this city and for his brother and sister firefighters.”

With reporting from The Dorchester Reporter