If a prank causes someone's death, what would the prankster be charged with?

He got cheated on and used by his HS girlfriend Mary Lou. She uses guys for fun. The scorned boyfriend wanted to get back at her with a stink bomb. It was meant as a prank.

However the prank backfired horribly, her dress quickly catches fire and she burns to death during her prom night ceremony. Obviously the guy is horrified seeing what just happened. He's even screaming for someone to help her. He only wanted to prank her, not burn her to death.

If someone's prank goes wrong and kills the person, what would he be charged with?

If a prank causes someone's death, what would the prankster be charged with?
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