Arson investigators on Monday began trying to determine what sparked a 5-alarm blaze that ripped through an abandoned building, which used to be home to KNTV's former news studios.
As soon as the sun came up, San Jose fire investigators started searching for clues as to how the building at 645 Park Ave went up in flames about 3 p.m. on Sunday.
The building had been abandoned for about a decade, after KNTV left the premises in 2004, though up to 30 homeless people set up camp inside there.
That's why investigators told NBC Bay Area they suspect the fire was started by a person, because there were many homeless people inside at the time who had brought in their BBQ grills, propane tanks and motorcycles.
There was some speculation from homeless people on Monday morning that another transient may have been responsible for the fire. Ace McCoy told NBC Bay Area that one homeless person he knew may have had a grudge against others because he had been asked to leave after he had been stealing from other transients in the building.
But no official word on the cause has been released, and arson investigators did not immediately respond to McCoy's allegation. Firefighters could not immediately tell whether the fire was started on purpose or by accident. Firefighters also used the building - which KNTV occupied from 1955 to 2004 - for training purposes.
Everyone was able to get out of the building safely.
But Ben Rapisure, who is homeless, said his friends "lost all their stuff. No clothes. Nothing. My heart goes out to them."
He added that the building had become sort of a "safe haven" for homeless people who gathered in the building for warmth and shelter. Rapisure was upset for his friends because he didn't know what they planned to do now.
Two firefighters were injured during the height of this fire. They were released and treated at the scene.
Neighbor Jacob Rangel said he ran outside of his apartment and started recording video of the blaze just minutes after the 5-alarm fire started.
"I just saw the whole place flaming up like there’s no way they could stop it," he said. "It’s too late."
Volunteer firefighter and photographer Craig Rose took a short group of clips of the fire.