PITTSBURGH (KDKA) – A fire on Margaret Street in Mt. Oliver Saturday night destroyed a family’s home.

There was a lot of smoke, a lot of damage, but no official cause yet.

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What investigators do know though, is that one firefighter was not supposed to be there.

He’s Francis Kestner Jr., the son of the Mt. Oliver Fire Chief – a former Mt. Oliver firefighter.

In a picture taken by a bystander, Kestner is seen in full gear.

KDKA’s video from the scene also shows Kestner there, not wearing a fire helmet.

Kestner was also arrested for arson about a decade ago. He was accused of – and later pleaded guilty – to setting fires at vacant home in Mt. Oliver, then rushing to put them out.

“There was injuries to innocent folks, as well as a couple firefighters during the course of putting out these fires,” said former Allegheny County Fire Marshal Bob Full back in February 2003.

Kestner is also a convicted sex offender and can be found on the Megan’s Law website. He pleaded guilty to sex assault charges in 2010.

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He is now on probation for arson and sex assault convictions.

Now investigators want to know why he was at the scene of the Mt. Oliver fire, who allowed him to take equipment from the fire department and who allowed him to be there. If he violated his probation, he can be sent to jail for doing so.

Community members also wanted answers at the borough’s council meeting Monday night.

The matter could be tricky since Kestner’s father is the fire chief, but his great-uncle is also the mayor.

“The fire department is already setting up the internal investigation, they have to get there board of directors together, which I understand is going to be done this evening or tomorrow,” said Mayor Jim Cassidy.

The subject wasn’t on the borough council’s agenda, Monday night. But it’s a subject they’ve dealt with before.

“I don’t think it’s too much of a conflict even though it’s his son,” Cassidy said. “Went through this — years ago.”

The mayor says he’s not sure how long it will take to get to the bottom of the issue, but he hope to have some answers in the next day or two.

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