(Reuters) - A video emerged online on Wednesday showing the moments before an unarmed black Florida man was shot by police as he lay in a street with his hands up next to an autistic patient whom he was trying to help, media reported.

Behavioral therapist Charles Kinsey was hospitalized after he was shot three times in the leg by a North Miami police officer during an incident on Monday, media said.

The incident comes at a time when racial tension is high in the United States. Protests have erupted in major U.S. cities during the past year and a half, as widely viewed videos of police shootings of black men drew attention to long-standing issues of race, policing and lack of accountability for officers.

Kinsey told WSVN-TV in Miami that he was trying to calm an autistic patient who had just ran away from an area group home. Kinsey said he found the patient sitting in a street playing with a toy truck.

A video that accompanied the news station's online story showed a black man in a T-shirt and shorts lying on his back with his hands up next to a man, who appears to have an object in his hand.

"All he has is a truck. A toy truck. I'm a behavior therapist at a group home," a man is heard saying in the cell phone video as police officers are seen with their weapons drawn.

The North Miami Police Department said in a statement that officers responded to a call of an armed suspect threatening suicide. Officers arrived at the scene and found an autistic man and an employee with an assisted living facility.

At some point during the on-scene negotiation, one of the responding officers fired his weapon, striking the employee, police said.

The moment of the shooting was not captured on the video and it is unclear why the officer fired his weapon.

An officer has been placed under administrative leave. An investigation is ongoing with the assistance of the Miami-Dade State Attorney's Office, the department said.

(This story corrects paragraph 7 to assisted instead of assist)

(Reporting By Brendan O'Brien; Editing by Nick Macfie)