LOUISVILLE, Ky. -- Authorities say four family members were killed in a murder-suicide at a Kentucky home that was set on fire.

Jefferson County Deputy Coroner Eddie Robinson said Monday the victims were a married couple and their two children. He says all four died of gunshot wounds.

Robinson says 33-year-old Brad Hettinger died at the scene Sunday of an apparent self-inflicted gunshot wound to the head.

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He says Hettinger's wife, 32-year-old Billie Jo Hettinger, died of gunshot wounds to the chest and head. He says her identification is tentative pending review of dental records.

Hettinger's wife also suffered thermal injuries in the fire, CBS affiliate WLKY reported.

Robinson says their children -- 5-year-old Collin Hettinger and 4-year-old Courtney Hettinger -- each died of a single gunshot wound to the head.

The victims were found in the home after firefighters responded to the fire in an upscale suburban neighborhood in southeast Louisville.

WLKY reported that investigators said firefighters did not know of the shootings until they found the bodies.

The coroner said the children were found in their beds, Billie Jo Hettinger was found in the basement and Brad Hettinger was found on the first floor of the home.

Jefferstontown firefighter Drew Hinton was off-duty Sunday, but hearing about what happened hit him, WLKY reported.

Hinton started an online donation page, to try and make things a little easier for the family of the victims.

"Help raise money for the family and friends for funeral costs and funeral expenses and any other unaccounted-for expenses they didn't expect," Hinton said.

The Louisville Fire Department union has also started a donation page.

"Hits close to home, so we kind of just want to help out as much as possible, and especially hearing that there was children involved," Hinton said.