A man fired from his warehouse job in April returned to his old workplace near Orlando, Florida yesterday and fatally shot five people before killing himself, Orange County Sheriff Jerry Demings said.

The 45-year-old suspect was armed with a handgun and knife when he entered a business called Fiamma, which describes itself as one of the world's largest manufacturers of awnings for recreational vehicles.

The unidentified assailant shot and killed five people before turning the gun on himself, Demings said at a press briefing. Three men and one woman died at the scene, and another man died at an area hospital. There was no indication that he used the knife on his victims.

The unidentified assailant had a history of misdemeanour criminal offences but was not linked to any terror organisations, said the sheriff, who described the shootings as workplace violence.

"He was a disgruntled employee that came back to this business this morning," Demings said. "It appears this incident has nothing to do with any global terror activities."

In June 2014, Orange County deputies investigated a report that the man battered another employee at the warehouse, but no charges were brought, Demings said.

The shooting comes almost a year after 49 people were killed at the Pulse nightclub in Orlando on June 12, 2016, the deadliest mass shooting in modern US history. At least 58 people were also injured.