The police officers involved in the shooting were responding to reports of an armed man threatening suicide, North Miami's police chief Gary Eugene told reporters on Thursday.
They acted "with that threat in mind," Eugene said.
At the scene, they found an autistic 27-year-old who wandered off from a nearby group home. A therapist from the facility was also there, trying to talk the patient into coming back.
The 47-year-old therapist Charles Kinsey laid down on his back and raised his hands up after the police arrived. His patient remained sitting beside him, playing with a toy truck.
"I am asking the officer, I said, 'sir, please don't shoot me. Please, do not shoot me'," Kinsey told WSVN-Channel 7.
A video taken directly before the shooting shows Kinsey laying down on the street, telling the patient to lie down and be still.
"All he has is a toy trunk in his hands ... I am a behavior therapist at a group home," he yells at the police.
The patient remains sitting on the curb, telling Kinsey to "shut up."
A police officer then fired three times, hitting Kinsey in the leg. The shots themselves, however, are not shown in the video. No gun was found at the scene.
'Like a mosquito bite'
"As long as I've got my hands up, they're not going to shoot me. This is what I'm thinking," Kinsey told WSVN from his hospital bed.
"When he shot me, it was so surprising ... It was like a mosquito bite, and when it hit me, I'm like, I still got my hands in the air, and I said, 'No, I just got shot,'" Kinsey said.
According to Kinsey, he asked an officer why he was shot and the officer replied, "I don't know."
On Thursday, US Attorney General Loretta Lynch said the Justice Department was looking into the case. Police said in a statement that the shooter was placed on administrative leave according to standard procedures.
Country on edge
At the press conference, police chief Eugene refused to identify the officers involved and answer reporters' questions.
"You have questions, the community has questions, we as a city, we as members of this police department and I also have questions," he said. "I assure you we will get all the answers."
He described the incident as a "very sensitive matter."
The US has seen a wave of protests over police shooting unarmed black men. Earlier this month, black shooters opened fire at the police in Dallas and Baton Rouge, killing a total of eight officers, including one African American.