The police officer charged with murder after a video showed him shooting a fleeing suspect in the back was allowed to stay on the force despite an earlier complaint that he used excessive force against an unarmed man, it has emerged.
When asked about his reaction to learning Michael Slager had been charged with murder, Mario Givens said: " It (the murder) could have been prevented. If they had just listened to me and investigated what happened that night, this man might be alive today."
Mr Givens said he was woken before dawn one morning in September 2013 by loud banging on the front door of his family's home in North Charleston, South Carolina.
On his front porch was Patrolman Michael Slager, the same officer now charged over the fatal shooting of Walter Scott, 50, following a traffic stop over a broken tail light.
The latest case of a white police officer killing an unarmed black man grabbed international attention this week after a video recorded by a bystander showed Slager firing eight times as Mr Scott ran away.
Wearing only a T-shirt and boxer shorts, Mr Givens, who is also black, said he opened his door by a crack and asked the officer what he wanted.
"He said he wanted to come in, but didn't say why," Mr Givens, now 33, told The Associated Press. "He never said who he was looking for." Then, without warning, Slager pushed in the door, he said.
"'Come outside or I'll Tase you,'" he recalled the officer saying as he burst in. "I didn't want that to happen to me, so I raised my arms over my head, and when I did, he Tased me in my stomach anyway," he said.
Mr Givens said the pain from the stun gun was so intense that he dropped to the floor and began calling for his mother Bessie, who was also in the home. Another police officer came into the house and they dragged him outside and threw him to the ground. He was then handcuffed and put in the back of a squad car.
Though initially accused of resisting the officers, Mr Givens was later released without charge.
"It was very devastating," said his mother, 57. "You watch your son like that, he's so vulnerable. You don't know what's going to happen. I was so scared."
It transpired that the police officers had gone to the family's home at the behest of his brother Matthew's ex-girlfriend, who earlier reported waking up in her nearby house to find Matthew Givens in her bedroom, uninvited.
Maleah Brown said she and a friend followed the police officers to the Givens' home and were sitting outside as Slager knocked on the door. The second officer had gone to the back of the house.
She had provided the officers with a detailed description of Matthew Givens, who is about 5ft 5ins. Mario Givens is well over 6ft.
"He (Mario Givens) looked nothing like the description I gave the officers," Ms Brown said. "He asked the officer why he was at the house. He did it nicely. The police officer said he wanted him to step outside. Then he asked, 'Why, why do you want me to step outside?' Then the officer barged inside and grabbed him."
Moments later, she saw the officers drag Mr Givens out of the house and throw him in the dirt, despite her yelling to the officers that they had the wrong man. Though Mr Givens was offering no resistance, she said she saw Slager use the stun gun on him again.
"He was screaming, in pain," she said. "He said, 'You Tased me. You Tased me. Why?' It was awful. Terrible. I asked the officer why he Tased him and he told me to get back."
Ms Brown said she later told a female police supervisor what she had seen.
"He was cocky," she said of Slager. "It looked like he wanted to hurt him. There was no need to Tase him. No reason. He was no threat - and we told him he had the wrong man."
Mario Givens went to police headquarters the following day and filed a formal complaint. He and his mother said several neighbours who witnessed what happened on the family's front lawn also contacted police, but officers refused to take their statements.
The incident report from that night filed by Slager and the other officer, Maurice Huggins, provides a very different version of events. In the report, obtained by AP through a public records request, Slager wrote that he could not see one of Mr Givens' hands and feared he might be holding a weapon.
He said he observed sweat on Mr Givens' shirt, which he perceived as evidence he may have just run from Ms Brown's home, and then ordered him to come out several times.
When Mr Givens did not obey, Slager said he entered the home to prevent him from fleeing and was then forced to use his stun gun when Mr Givens struggled against him. According to the officers' report, the Givens brothers are described as looking "just alike".
After Mario Givens filed his complaint, the department opened an internal investigation. A brief report included in Slager's personnel file said a senior officer was assigned to investigate. After a couple of weeks, the case was closed with a notation that Slager was "exonerated".
Mr Givens said he was never contacted as part of the internal investigation into Slager and only learned the case had been closed after he went to the station about six weeks later and asked what happened.
North Charleston police spokesman Spencer Pryor said the department planned to review the case to see if its decision to exonerate Slager was correct.