Meanwhile, Montaie, who is Cain's neighbor, continued to record the arrest, saying, "Oh Jesus, I've seen this, Lord".
The preliminary investigation also showed the officer had no adequate grounds to make the initial stop.
"It was supposedly for jaywalking", Cain said of the initial arrest.
Police say "the pedestrian began removing his jacket, challenging the officer to fight". 'Oh Jesus! I seen this, Lord. Oh my God. He beat him like that!
The officer involved has been put on paid administrative leave pending the outcome of an internal investigation.
On Tuesday, the Police Department released dash-cam video footage from the officer's patrol cruiser showing the confrontation.
The woman shooting the video from her vehicle yells, "Nephew just listen", about 3 seconds before the officer steps forward and pushes the man to the ground. At that point, the officer charged the man to take him into custody.
KTXL spoke with a witness who saw the incident, and she said she felt everything was wrong with the way the officer handled the situation.
After some words are exchanged while Cain is standing in the street, the officer then violently throws Cain to the ground and begins to punch him in the head.
The officer, who is white, confronted Nandi Cain Jr., after he had allegedly been jaywalking, a violation in the state of California.
"So I took off my jacket to let him know, 'I don't have anything, '" he told the news station. He was released early that morning, however, after the resisting charge was dropped. "I thought, as soon as they got me on the ground and they start putting my arms in different positions".
"There has been a history of the police not being trusted to do the right thing but in this particular case we have received a response that we like and expect from our police department".
Sacramento Police called the violent encounter "unacceptable conduct" and said a personnel and criminal investigation had been launched into the officer's actions.