The bodies of the firefighters left from Duggan's Serra Mortuary in Daly City and are making their way up to San Francisco. Each casket is being carried on a fire truck. Several streets around St. Mary's Cathedral have been blocked off.
The mass will be celebrated by Archbishop George Niederauer as well as three chaplains from the San Francisco Fire Department. Relatives of the firefighters will also take an active part in the mass.
Sergeant Lucio Perez of the SFPD, brother of Vincent Perez will do the first reading. Jaqueline Valerio Samsel, Anthony Valerio's sister will handle the second reading. Friends and relatives will speak along with Mayor Ed Lee and Fire Chief Joanne Hayes-White.
The caskets will leave St. Mary's at about 3:30 p.m., accompanied by an honor guard and pall bearers made up of family members. About 150 to 200 fire engines will take part in the procession. The service is open to the public.
St. Mary's has a seating capacity of about 2,400, but 5,000 to 6,000 are expected. There is an overflow area in the cathedral as well as a place the public can see a live video presentation at the Sacred Heart Cathedral auditorium on Ellis Street.
Last night, hundreds gathered at St. Mary's Cathedral for a vigil. It was a joint service, which will also be the case for Friday's funeral.
Perez and Valerio died of injuries suffered while battling a house fire in Diamond Heights last Thursday, becoming the city's first firefighters to die in the line of duty in 16 years.
"We mourn them, we celebrate them. Our hearts are heavy and we're going to get through this," said San Francisco Fire Department Lt. Ken Smith.
The service will be televised in its entirety starting at noon on ABC7 and is being streamed online.