The fire erupted Tuesday at the city library in Porterville, California.

A second firefighter has been found dead in a powerful arson blaze that ripped through a California library, leaving a fire department in mourning.

The fire — allegedly started by two 13-year-old boys — erupted Tuesday at the city library in Porterville, about 80 miles southeast of Fresno, authorities said.

The books and furniture ignited quickly, making the fire especially difficult to fight, officials said. The blaze eventually caused the ceiling to collapse into the building, officials said.

Porterville Mayor Martha Flores called the firefighters “heroes” whose deaths are “tragic, horrific and devastating.”

Porterville Fire Chief Dave LaPere choked back tears Wednesday as he announced that one firefighter killed was identified as 35-year-old Capt. Raymond Figueroa, who had been with the department since 2007.

Firefighter Patrick Jones, a 25-year-old with the department since 2017, was unaccounted for through Tuesday night and all day Wednesday.

Wednesday night, Jones’ remains were found within the library, officials said.

All Porterville firefighters are taking the week off and are being allowed time to evaluate their mental health, LaPere said Thursday.

“They’ve been offered counseling,” he said.

“In this difficult time,” LaPere said, the department is grateful for “the encouragement and sympathy from our community, other agencies, legislators and the public at large.”

Two 13-year-old boys “did start the fire intentionally,” Porterville Police Chief Eric Kroutil said at a news conference Thursday. “This is a homicide case.”

The boys were booked as juveniles on charges of arson, conspiracy and manslaughter, he said.

Police will meet with prosecutors Thursday afternoon to determine “what is next in the process,” Kroutil said.