My dad is a ninja

It was Career Day at school, and every child in Miss Claire’s class brought their father in to show off.
Susie’s father was a fireman.
Abdul’s father was a lawyer.
Johnny’s father was a baseball player.
Bobby’s father was… absent?
“Where is your father, Bobby?” asked Miss Claire.
“He’s lurking in the shadows,” said Bobby.
“Why?”
“Because he’s a ninja.”
“He’s not a ninja.”
As fast as lightning, a fist plunged through Miss Claire’s chest, ripped out her heart, and showed it to her before she died.
“See?” said Bobby.
Oh, did I mention that Susie’s father was a fireman?