Abdirahman Abdi, a Somali immigrant described as a gentle man with a mental illness, has died following a bloody altercation with Ottawa Police.

Ontario's Special Investigations Unit is probing Abdi’s arrest on Sunday, which is leading to accusations of police brutality and anti-black racism.

Witnesses said several police officers were involved in the arrest and that they used batons to subdue Abdi in front of the non-profit building where he lives.

"They were really, really going at him and he was screaming," said David Thyne, who said he watched the situation from his balcony across the street.

Abdirahman, 37, was cuffed when he was being beaten, Thyne said. "He was pleading with them to stop."

Miriam Ali said she went outside after hearing screaming and saw a man lying on the ground.

"He was unconscious and he was sitting in a pool of blood…I came out here and he was lying on his front and there were just like five of six police officers on him," she said.

'Gentle young man'

Family friend and neighbour Nimao Ali took cellphone video after the arrest that shows Abdi on the ground in handcuffs, with two officers standing over him administering first aid.

She told CTV Ottawa that the family has asked for prayers.

“I’m speechless right now,” she said. “We’re devastated by the loss of such a decent, nice, gentle young man in our community. I can’t find the words right now.”

Neighbour Shukri Samater described Abdi as pleasant and non-violent. She said she arrived after he was cuffed and on the ground, and there seemed to be a delay before police started administering first aid.

"We're all very concerned because he was somebody who was mentally ill. I have a sister who has Down syndrome. She lives in the building. A lot of people are wondering who's next, so they're very scared."

Samater says the community usually has good relations with the police and that they're generally able to de-escalate a situation.

"I'm just worried that this might set a precedent, especially for people who can't really communicate their feelings," she said.

Police said Monday that they responded around 9:30 a.m. to a disturbance at a local coffee shop. They then chased the suspect by foot. They would not comment further, citing the SIU investigation.

The SIU statement says Ottawa police were called to a disturbance in Ottawa's Hintonburg neighbourhood, a few blocks from Abdi's residence in a building run by the Ottawa Community Immigrant Services Organization.

"At some point during the confrontation, the man suffered medical distress," the statement said.

The SIU investigates reports involving police where there has been death, serious injury or allegations of sexual assault. The SIU is urging anyone who may have witnessed the incident to contact the lead investigator at 1-800-787-8529.

Accusations of police brutality

Somali Canadian and Black Lives Matter supporter Hana Jama said although “we don’t know anything” about what happened, “at the same time, we do know that the man who was beaten up by police was a black man, was a Muslim man, was a Somali man and was a mentally ill man.”

“That should be enough to know that happened to him was messed up,” Jama added.

Alicia LeJour, from the activist group No Justice No Peace, said it was “clear that this man was in good condition until he came into contact with police and he was suddenly bleeding and on the ground.”

“I’m not too sure how they classify that as a medical emergency as opposed to police brutality,” she added.

Criminal defence lawyer Leo Russomanno said it appears to be yet another example of police “resorting to excessive use of force” and “perhaps our frontline officers being inadequately able to deal with people with mental health issues.”

Councillor: don't 'jump to conclusions'

Jeff Leiper, the area's city councillor, wrote in a blogpost that he arrived at the apartment building as the ambulance left, and spent five hours there speaking with family, residents and witnesses. He also spent some time at the hospital.

"Several descriptions have been provided of the police striking [Abdi], which need to be investigated. There have been multiple accounts given that he has a mental illness, and that mental capacity likely played a role in today’s events," Leiper wrote.

Leiper added that he was left “disturbed” by what he heard from residents, but that it is “critical that (the SIU) finish their work.”

“Today’s incident raises many questions,” he went on. “Conflicting information is circulating, and the potential to spread misinformation is high. I have every confidence that the civilian SIU will investigate this thoroughly, and I would ask residents to wait for the results of that process before jumping to any conclusions.”

'No excuse': defence lawyer

Ottawa lawyer Michael Spratt, who has handled cases involving excessive police force but isn't directly involved with Abdirahman's case, says he's concerned about some of the early reports on the arrest.

"There are often times injuries incurred trying to arrest someone in a dynamic situation, but the reports of gratuitous violence after handcuffs were placed on the individual [are] shocking and there can be no excuse for violence after the person is handcuffed and on the ground," Spratt said in an interview with CTV News.

"The lack of immediate medical attention and the reports about the delays between when first aid was administered and when paramedics arrived is troubling as well. When a subject is detained and handcuffed and has been beaten into unconsciousness, there can be no reasonable reason why medical attention should be delayed."