Alvaro Zabaleta of the Miami-Dade Police Department said in an email to news organizations that detectives were called to the scene of a shooting along South Lejeune Road in Coral Gables.
Another trainer at the fitness center told one of his members the shooting involved a disgruntled former employee.
Benedicte, the woman at the gym, described the shooter as a tall, muscular African-American man.
Police said the shooter is dead, The Miami Herald reported - and it is believed that he committed suicide after firing his gun.
Anais Michelle said she was walking into the mall with her mother when she saw people coming down from the third level, some crying about a shooting at the gym.
A gunman opened fire inside an Equinox fitness club at the Village of Merrick Park in Coral Gables, Florida, around 1 p.m. on Saturday - leaving two people injured, multiple outlets report. "There was a dance class of 40 people if he wanted to do that".
Masters 2017: Charley Hoffman leads after first round; Dustin Johnson withdraws
Johnson was still trying to digest the last 24 hours, as shocking as any for a No. 1 player going into a major. Then again, he pointed to a poor British Open record, adding, "I've also played disgusting in the wind".
Witnesses at the nearby Soul Cycle heard several gunshots.
"They said run, and I ran", said the woman, who declined to identify herself to an AP reporter.
"So that's exactly what we did", said Tim Hartog, the restaurant's general manager.
"We had everyone underneath tables and got everyone to the back", he said.
The scene is now secure, according to the Miami Dade Police Department, but the stores at the mall will remain closed. On April 8, 2017, there was a shooting at the Equinox gym at the shopping center.
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