Investigators work the scene of a fatal workplace shooting in Orlando, Florida, U.S. June 5, 2017. [Photo/Agencies]

Nearly a year ago, a gunman claiming allegiance to the Islamic State militant group killed 49 people at the Pulse nightclub in Orlando, the deadliest mass shooting in modern US history.

Demings said the incident on Monday morning lasted just minutes.

At one point, Neumann told a temporary employee he did not know to leave the premises. He reloaded his handgun, for which he did not have a permit, at least once during the incident and killed himself as deputies were about to enter the warehouse, the sheriff said.

Law officials were seeking a search warrant for Neumann's home in the area, where he lived alone, Demings said.

Neumann was honorably discharged from the Army in 1999 and had a history of misdemeanor criminal offenses, such as possession of marijuana and driving under the influence.

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

Reuters