Two men killed a 50-year-old social worker in a brutal attack over fitness equipment in a Brooklyn gym, according to police.

Douglas Smith was murdered after a dispute over who had dibs to a Nautilus elliptical machine at the Church Avenue Fitness Club in East Flatbush. After exchanging words with a "bodybuilding buff standing more than 6 feet tall, and a younger scrawnier club member," Smith's rivals summoned two men from outside the gym to attack him, the Daily News reports.

The perps approached Smith from behind as he worked out on the elliptical machine and stabbed him three times in the back before hitting him on the head with the hammer. Smith — who had recently earned his master's degree in psychology and spent his days providing aid to parolees — died at Kings County Hospital on Sunday morning. Cops have nabbed one suspect, 19-year-old Shawn Hing, who is accused of striking Smith with the hammer. He is facing a charge of second-degree murder and is being held without bail. Another suspect remains at large.