Robert Seman Junior was due to face court for the murders of Corinne Gump, 10, and William and Judith Schmidt.
The family were killed in their home in Youngstown, Ohio, in March 2015 just hours before the 48-year-old was due to stand trial for raping the youngster.
CCTV camera captured the moment Robert Seman Junior leapt to his death
Seman Jnr was accused of starting the fires deliberately to avoid the child, after he was found covered in burn injuries – with two gas canisters discovered in his home.
But despite overwhelming evidence against him, the accused paedophile pleaded not guilty and was due to stand trial on Wednesday.
But following his final court hearing, a CCTV camera captured the moment as he leapt to his death.
Robert Seman Junior was faces charges of murder and rape
I think it’s very telling. He knew the evidence against him.
Dawn Cantalamess, lead prosecutor
The shocking footage shows Seman Jnr walking through an empty courthouse corridor accompanied by two burly security officials.
As they walk along, the killer took his chance and threw himself over the fourth-floor balcony wall.
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Robert Seman Junior was due to face court for allegedly raping Corinne Gump
Courthouse staff rushed to his side, where a lawyer felt for a pulse but paramedics soon declared Seman Jnr dead at the scene.
One official said: “That was an evil, evil, man.”
The killer threw himself over the fourth-floor balcony wall
Dawn Cantalamess the lead prosecutor later added: "I think it’s very telling.
"He knew the evidence against him.
"Every witness we talked to in preparation for the case, they didn’t know why he wasn’t pleading guilty or asking for some sort of plea, so this is very telling."