More than a hundred protesters have gathered in Newport following the death of a man shortly after police were at his house.
Moyied Bashir died on Wednesday after officers were called to his home in Newport at about 09:00 GMT.
The force has referred itself to the Independent Office for Police Conduct (IOPC) following the death, as is standard procedure.
It said the 29-year-old’s condition worsened after they arrived.
He was pronounced dead at Cwmbran’s Grange Hospital.
Protestors walked through Pill and gathered outside Newport’s central police station on Thursday.
They banged on the door, shouting “we want answers” and “we want justice”.
The protest was led by Mohamed Bashir, Moyied’s brother, who said his parents, Mamoun and Mahasin Bashir, had called the police on Wednesday, looking for help.
“My brother was stabbed about three weeks ago, he was put on medication,” Mr Bashir said.
“He’s been battling mental health for a long period of time.
“The combination of the medication and his mental health, it got a bit stressful.”
He said his parents decided to take him back to hospital but could not get him out of his room.
“They believed their best option was to call the police and help them escort him to hospital,” Mr Bashir said.
“They rung the police with the intention to escort him to hospital with, say, two to three officers.”
But, he said, 24 officers arrived and “forced” their way into his room,
He said police handcuffed him and “tied him up by his leg”.
“His stab wound is on his main artery, so while he is tied up, handcuffed, he started getting weaker,” Mr Bashir said.
“My dad is in shock (saying), ‘What are you doing?’
“In hospital, my brother was given CPR, oxygen, they tried everything. It was too late. We only wanted help.”
His brother was a “big character, the life of the party” and someone who “wouldn’t harm a fly”, Mr Bashir said.
He said he was angry his brother had died, just a month after concerns were raised about another black man’s death, Mohamud Mohammed Hassan, hours after he left custody in Cardiff.
Mr Bashir said: “It’s disgusting, there needs to be something done. It’s been happening for so long.
“Serve and protect that’s what they tell us. We are going to fight. We are going to get answers.”
Mohamed Bashir called on Gwent Police to release any bodycam footage the officers who went to his parents’ house would have been wearing.
“My parents are heartbroken,” he said.
The IOPC said investigators visited the Bashir property. It said officers involved had their initial accounts of what happened.
The watchdog said: “We are aware that Mr Bashir, who was not arrested, was initially handcuffed and leg restraints were applied at the property while an ambulance was awaited.
“During their interaction with Mr Bashir his condition was noted to deteriorate.
“Paramedics arrived and gave medical treatment at the address prior to moving him to a waiting ambulance.
“We have established that by the time the ambulance had arrived a number of police vehicles and nine police officers had responded to the incident.”
It added it was “securing” bodycam footage, police radio transmissions and call logs for analysis.
Gwent Police said when they arrived at the family’s home “a 29-year-old man appeared to be suffering a medical episode”.
“Officers called an ambulance and he was taken to the Grange Hospital where he was pronounced deceased a short time later.”