Rochester Police are under fire for detaining and pepper spraying a child who'd been reported as suicidal, and body cam video of the incident is disturbing.

Officers had handcuffed the 9-year-old girl during the Friday domestic violence call. Police say her mother was worried the girl would harm herself or others. While walking the child to a patrol car, she fell to the snowy ground, began flailing arms and screaming she wanted to see her dad.

A nearly 10-minute struggle ensued ... as the girl resisted, 2 officers put the cuffs on her and attempted to put her in their car. The girl continued screaming and said she wouldn't get in until she saw her dad.

A female officer stepped in, trying to convince her to get in the backseat. A male officer, who was trying to pull the girl in from the other side yelled, "Sit up! You're acting like a child, stop" -- to which she responded, "I am a child!! What the f***?"

The female officer eventually warned the child the cops were getting impatient, and she would be pepper sprayed if she didn't get in the car. Less than a minute later, a male officer said, "Just spray her at this point" ... and that's what happened.

The full arrest video includes a disturbing interaction with the child's mother, and you hear the girl accuse her mother of stabbing the father ... which the mother denied.

Rochester PD initially said it was "required" to deploy pepper spray -- but over the weekend Rochester Mayor Lovely Warren said, "This video, as a mother, is not anything you want to see."

Civil rights attorney Ben Crump has taken notice of how police treated the 9-year-old, saying, "You cannot justify this!"

Police announced an internal investigation, but haven't said if any of the involved officers have been suspended. The child was treated at a hospital and released to her family.