Five people killed in workplace shooting in Orlando
Orange County Sheriff Jerry Demings said the gunman, 45, was a disgruntled former employee at Fiamma, a business that makes awnings for recreational vehicles, who was fired in April.
Mr Demings said the gunman, who was also armed with a knife, shot and killed himself at the scene.
There are no links to terrorism.
The gunman, who has not yet been identified, had been involved in a previous incident of workplace violence and had been accused of attacking another employee inside the business. He was not charged in that case.
Mr Demings added: “This is a sad day once again for us in Orange County. Our hearts go out to the victims.”
Shelley Adams’s sister Sheila McIntrye works for the company and was in the toilet when shots rang out.
Ms McIntyre is safe but she called her sister during the shooting.
She kept repeating “My boss is dead, my boss is dead”, Ms Adams said.
Florida governor Rick Scott said in a statement that “all Floridians pray for the families impacted by this senseless act of violence”.
He said the Orlando community has been challenged like never before, a reference to the shooting on June 12 last year at the Pulse nightclub in the city in which 49 people were shot dead in the worst mass shooting in modern US history.