Action News has learned that Slivinski apparently took his own life.
Police, meanwhile, confirm a suicide took place in Slivinski's block, but they have not released a name.
Tip callers tell Action News that medics responded to Slivinski's Lawndale Avenue home before dawn Saturday morning.
Philadelphia Fire Commissioner Lloyd Ayers has confirmed that he died, but would not say how or where.
Slivinski is the 31-year old firefighter who got into trouble in April for posing for a calendar wearing only his bunker pants.
The calendar was called "The Nation's Bravest," and proceeds were to go to widows of local firefighters, but fire Commissioner Roy Ayers disapproved.
Slivinski was given a pay cut, removed from the elite Rescue One unit, and reassigned to a regular fire house. He was given his job back in May.
Katherine Kostreva, the woman who was producing the calendar, issued a statement saying, "I am blessed and honored to have met Jack. As a Marine, firefighter, loving son, brother and friend, he cared only for the well being of others. His fortitude and courage is an inspiration and I grieve the loss of a friend. God bless him."
Firefighters Union Local 22 President Bill Gault released the following statement:"Dear Brothers and Sisters,
You may have heard that Local 22 and the Department have lost one of our own this weekend. Firefighter Jack Slivinski sadly lost his life early Saturday morning.
We are all shocked and at a loss to express our extreme sadness to this terrible event.
Our thoughts and prayers are with the entire Slivinski family.
Jack was a valued member of Rescue 1 where Jack was well known and well liked. Jack, like many of you, had a big heart and spirit of giving.
These are difficult times for all of our members. Please be considerate of one another and be supportive of all through this time of loss and mourning.
Jack was a kind hearted and extremely generous young man whose first instinct was always to put others first.
All of us, this Department and this City have lost one of its finest sons.
When final arrangements have been made, Local 22 will inform all members."
