''That's the point when the screaming stopped … I thought he fainted,'' a witness told the Herald yesterday. ''I didn't think the man would die.'' But he did. The last minutes of the young man's life are now the subject of an investigation by homicide detectives, and a swirling debate about police use of Tasers. The use of the stun gun might have been in breach of NSW Police Force guidelines to use the weapons in incidents where their lives or those of fellow officers are in jeopardy - when ''violent confrontation or resistance is occurring or imminent''. Last night police sources said they had contacted the young man's family in Brazil but formal identification had not yet taken place. An autopsy is expected to be carried out today and toxicology tests conducted to reveal whether drugs or alcohol had played a part in his conduct, police said.

The witness, who has spoken to police but asked not to be named, said he was getting out of a taxi when he saw police chase the man across Pitt Street about 5.30am on Sunday. ''The man was topless and he was running as well as he could,'' he said. ''His pants were falling down. I thought he was just drunk … and the police were trying to catch him.'' The witness said police tackled the man against a wall outside a cafe. ''So [then] I thought he was some serious criminal or something. He was struggling … there was a lot of physical involvement from the police. ''He was on the ground already and they were holding him down. He was screaming and there was a lot of sound from the Taser. At one point I heard him scream out, 'Help me, and he kept screaming and was trying to fight back.'' The witness said he heard three or four Taser ''zaps'' during the struggle.

But then the screaming stopped. ''I thought he fainted,'' the witness said. Police believe the man was under the influence of drugs and probably alcohol at the time of the attempted arrest but they are still trying to confirm whether he was the person involved in an incident about half an hour earlier at a convenience shop in King Street. A witness there said a man had entered the shop twice, was ''frothing at the mouth'' and had tried to jump over an internal door before being chased out of the shop. The Premier, Barry O'Farrell, and the Police Minister Michael Gallacher, reaffirmed their support for the use of Tasers. ''It is a concern that a person has died,'' a spokesman for Mr Gallacher said last night. ''However, we must allow a proper investigation to be carried out and we must also await the findings from the coroner.''

The NSW Greens MP David Shoebridge said a steep increase in the weapon's use means questions must be asked about whether it was being deployed appropriately. In 2008 the Taser was used 126 times and this rose to 1169 times by 2010. But last year the figure dropped to 826. The NSW Ombudsman, Bruce Barbour, said the debate had ''moved on'' from whether Tasers should used at all, and should focus on whether they were used in an ''appropriate, reasonable and proportionate'' way. Loading ''When properly used, they are a very useful option for police,'' he said. ''They are not supposed to be used as a compliance tool.''

with Anna Patty