If you believe what Joe Passalaqua says, he was one of the most prolific hitmen in mob history.

By day, a beloved gymnastics coach -- by night, a cold-blooded criminal. Passalaqua claims he was a private enforcer for legendary crime boss John Gotti. But the feds say his story is full of holes. Is this gym coach a mob killer or a con man?

Joe Passalaqua came to be known as "Steroid Joe."

David Kushner, the journalist who uncovered this good-guy-gone-wise-guy story, says Passalaqua was always looking to be bigger than life. And gymnastics was his way to be a big shot. Passalaqua opens a successful gym called Flip Over Gymnastics. But he's still hungry for something even bigger.

"He started seeing guys come into the gym who, as he put it, 'looked like King Kong' and he wanted to know what were they doing," said Kushner.

What they were doing was steroids, and for Passalaqua it becomes a habit that spins dangerously out of control.

"He felt it made him into what he said was a violent animal," said Kushner.

Passalaqua's friend and fellow trainer Blair Gaertnier saw it firsthand.

"He could be the nicest guy in the world and then he could be the biggest jerk in the world," said Gaertnier.

Passalaqua steroid-fueled rage gets the attention of unsavory elements outside the gym. Passalaqua claims a shady acquaintance of his said there was someone he should meet.

"Joe says this restaurateur then took him to Little Italy and they went to small social club where he was led into a room, and there, sitting behind the desk, was John Gotti," said Kushner. John Gotti, the notorious crime boss who fought his way to the top of Gambino crime family through ruthless tactics and cold-blooded murder.

Was this lowly gym coach invited to join the infamous Gambino family by Gotti himself? From lockup in Cumberland Federal Prison, Passalaqua says yes, and he was given the nickname "Angel," putting himself center-stage in the kind of mob stories that would make Hollywood jealous.

Joe Passalaqua says his association with Gotti would send him down some dark roads. But are his crime stories as pumped up as he is? The FBI tells Crime Watch Daily that Joe Passalaqua isn't who he says he is.

Do you believe Joe Passalaqua was a Mafia hitman, or just a storytelling convict? Sound off in the comments below.