A fifty-year-old man working out at a New York gym last Saturday was stabbed to death in the back over the use of an exercise machine.

Witnesses said Douglas Smith and a fellow gym member at the Church Avenue Fitness Club were fighting over who was next on a Nautilus elliptical machine when the man, who was quarreling with Smith, phoned two of his friends and told them to come over to the gym.

When the men arrived at the gym they saw Smith working out on the machine and approached him from the back and stabbed him three times before hitting him in the head with a hammer.

Smith, who worked as a social worker and moonlighted as a bouncer at a bar, was rushed to Kings County Hospital where he died Sunday.

Speaking to local media, his father, Castello Smith said he found out about his son’s murder when the police showed up at this home Monday night.

“I wish I could have been with him at the hospital,” the elder Smith said.  “I would have said to him, ‘Dougie, this is your daddy.”

Brooklyn police arrested 19-year-old Shawn Hing Sunday night and charged him with second-degree murder.

A manhunt is still on for Hing’s accomplice and the gym member who called the killers to the gym.