Hundreds showed up at St. Mary's Cathedral for the night's vigil. It was a joint service, which will also be the case for Friday's funeral.
It was a somber moment when the bodies of Perez and Valerio arrived late in the afternoon and standing in tribute were their fellow firefighters of the San Francisco Fire Department.
By evening, hundreds gathered inside the cathedral for a vigil in their honor. 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 Lt. Ken Smith.
Valerio was 53 years old. Perez was 48. Mayor Ed Lee says dealing with their deaths has so far been the hardest part of his job.
"Budget, pension, everything that's, it's nothing compared to the need to understand what these folks go through, what they do every single day and being there at the hospital twice, was the hardest thing I had to do," said Lee.
As for Friday's funeral, as many as 6,000 people are expected to attend. Many will be firefighters from all over the country, including Taylor Gaskins of the L.A. Fire Department. He says he remembers when San Francisco firefighters attended his colleague's funeral a few months back.
"I was like, 'Wow, those guys came down here to support us when Glen Allen died, so it's important for me to do the same,'" said Gaskins.
And to make sure every San Francisco firefighter will be able to attend, crews throughout the Bay Area will be filling in for those who are scheduled to work.
"So that's huge. We've never done that in this city before where we have other agencies coming in and so that in and of itself has required a lot of planning, but I feel good that anyone that's on duty that really wanted to be here could be here tomorrow. I think that's important," said San Francisco Fire Chief Joanne Hayes-White.
News of Perez and Valerio's death have spread beyond U.S. borders. ABC7 learned even firefighters from Canada will be attending Friday's funeral.
The funeral will begin at 12:30 p.m. Friday at Saint Mary's Cathedral. The service will be carried live in its entirety starting at noon, both here online and on ABC Channel 7.