Ayers said that he did not know whether Slivinski, 32, had left a suicide note. The fire commissioner said that he was awaiting a final investigation report from police.
A police source told the Daily News that the firefighter had used a .40-caliber weapon and discharged it from under his chin.
"It was totally sudden and unexpected," Kostreva said. "It was everything he was not."
The New York photographer had inadvertently pushed Slivinski into the limelight in April when Fire Department brass learned that Slivinski had posed shirtless for Kostreva's charity beefcake firefighter calendar. Ayers subsequently removed him from his post with the elite Rescue 1 unit because of the photos, but Slivinski was reinstated less than a week later.
"It's tragic," Ayers said yesterday. "It's shocking. It's all of those things. A young firefighter with all the potential . . .
"Our support and prayers are with them," Ayers said of Slivinski's family. "We're making sure they can go through this. It's just hard."
Slivinski's family informed Bill Gault, president of Fire Fighters Local 22, that they would not comment to reporters.
"We don't have any answers for this," Gault said. "He had the world in front of him. It's a terrible tragedy. We mourn the loss and are praying for his family. They're taking it very hard."
Besides his father, Slivinski is survived by his mother, Geraldine, and his wife, whose name was not available. Kostreva said that Slivinski, with whom she corresponded almost daily and spoke frequently, was separated from his wife.
"You meet him for a second and you're already captivated," Kostreva said. "It was never about him. It was always about family and sacrifice, but it was never about him."
She noted that he had served with the Marines before he entered the Fire Department in 2002.
"I'm blessed to have met him," Kostreva said.
When Ayers transferred Slivinski out of Rescue 1, "it was tough on him," Kostreva said. "It really, really hurt him."
Nonetheless, "he was so positive. It was like me and him versus the city. He was like a champion. He had that spirit the entire time."
The photographer came from New York during his troubles and, with his parents, walked around the Piazza to collect signatures for a petition asking that he be reinstated. They collected 1,001 signatures, Kostreva said.
Members of the Facebook page "Mr. Philly Jack Slivinski," started by Kostreva when he was transferred out of his job, posted prayers and sympathy notes all weekend to Jack and his family.
From Mike K.: "Rest peacefully Jackie. gone way too soon, but the lives you touched and saved should all be thankful for knowing you."
Viewings will be from 6 p.m. to 9 p.m. tomorrow and from 8 a.m. to 9:30 a.m. Wednesday at the Burns Funeral Home, on Frankford Avenue near Grant, in Torresdale.
A funeral Mass will follow at 10:30 a.m. Wednesday at St. Timothy's Church, on Levick Street near Battersby, in Mayfair. Burial will be at Westminster Cemetery on Belmont Avenue in Bala Cynwyd.