A man has died after police shot him with a Taser, Greater Manchester Police said.
The 23-year-old named locally as Jordan Begley suffered a "medical episode" and died after police fired at him with the stun gun.
Officers were responding to a disturbance at around 8.15pm on Wednesday night in Gorton, Manchester, when they used the Taser to detain the man.
The police force has referred itself to the Independent Police Complaints Commission.
Assistant Chief Constable Garry Shewan said: "Police received a 999 call reporting a disturbance on Beard Road in Gorton where there was a man with a knife.
"Officers were dispatched immediately and arrived in eight minutes.
"On arrival, a Taser was discharged to detain a 23-year-old man.
"At this time it is unclear what happened, but at some point afterwards the man suffered a medical episode.
"Paramedics performed first aid on the man at the scene before he was taken to hospital where he sadly died."
The death has been referred to the local coroner and police family liaison officers are supporting the family.
A police cordon surrounded 10 terraced houses at the end of Beard Road.
A forensic tent was placed in the road within the cordon which was guarded by uniformed officers, a police van and two patrol cars.
A friend of the dead man said that eight armed response officers attended the family home on Wednesday night.
"They turfed his mum outside and then went in and battered him," said the man, who did not want to be named.
"There were about eight armed response officers went in.
"He didn't have a knife though. I know for a fact he would not have had a knife.
"There was no need to use a Taser on him. I think he has some problem with his heart."