This video shows a suspected drug-user being restrained by three police officers - only for him to lose consciousness and be pronounced dead.
The two-minute-long footage shows the male suspect being pinned to the ground, his head pushed to the pavement until he appears to stop breathing.
It was captured by a passer-by on his mobile phone in Bedford town centre on Wednesday lunchtime.
Bedfordshire Police confirmed a man had died at the scene, and that the incident had been referred to the Independent Police Complaints Commission (IPPC).
Eyewitnesses said that ‘four or five’ plain-clothes officers jumped out of an unmarked van and chased the man, who has been named locally as Carl Brunner.
They then tackled him to the ground while “one officer had his hands around his throat”, an onlooker said.
In the video, filmed by a bystander, they can then be heard shouting, “Spit it out, spit it out,” as they hold him down with their knees on his back and hands on his head.
Seconds later the man, who is thought to be in his fifties, appears to slip out of consciousness and his head slumps to the side.
Blood then poured from his mouth, an eyewitness said, and officers noticed something was wrong.
But while the police appeared concerned shocked onlookers said they searched the man’s pockets - despite him having blacked out.
The footage then shows officers putting him in the recovery position and performing CPR.
Paramedics also attended the scene but the man died, Bedfordshire Police said.
An acquaintance of the man witnessed the drama unfold on Midland Road, Bedford at around 12.30pm on Wednesday.
The 47-year-old, who asked not to be named, said: “I was just walking to the shop and then I saw four or five men.
“These burly guys all went up to this old man, in his fifties or so. They didn’t really run but they grabbed the guy, who couldn’t run anyway.
“They brought him to the ground. I think he put something in his mouth and they were trying to get him to spit it out.
“They had their knees on his back and were holding him down.”
They added: “They were pushing him down. They had his head on the pavement.
“They were saying, ‘Spit it out, spit it out.’ Then he went unconscious and blood started coming out of his mouth.
“He was out - completely out. They were searching his pockets while he was out. Then they backed off.
“They asked me to turn my video off but I didn’t. There were lots of other people around and there is a camera straight opposite, a CCTV camera.
“I think he was being chased for something to do with drugs. That’s why they had him on the floor.
“But there is no way that if he swallowed drugs then all that blood would have gushed out of his mouth afterwards.
“It was crazy. They were worried about themselves.”
Another witness to the incident said: “The police tackled him to the ground and he seemed to smash his head off the floor.
“Then they tried to perform CPR.”
Police have since confirmed the man died at the scene.
The police watchdog, the Independent Police Complaints Commission (IPCC), has been informed and an investigation launched.
Friends of the deceased, believed to be a Canadian man who is nicknamed Yankee, said Bedfordshire Police have a “lot of questions to answer”.
Writing on Facebook, Arron Davies said: “Rip Yankee Carl brunna died by police tackle bash to the head u were good guy Yankee and will be missed.
“So sad. Bedford police got lot questions to answer.”
When asked what happened, he added: “Some guy midland rd guy got a brother who stabbed somone in chest in the summer over a zoot or summink like that. “He always on midland but he was calm good guy humble.”
Another commenter, Matt Elderkin, said: “Bully Boy Police Tactics. Bedfordshire Police should be ashamed.”
Paying tribute to his friend, Clive Leybourne said: “He used to sit in the same spot quietly having a drink watching the world go by.
“He was softly spoken and always glad to have a chat and a bite to eat with me. I shall miss him.”
A Bedfordshire Police spokesman said: “Officers gave first aid at the scene and the ambulance service also attended, however the man has sadly died.
“The IPCC will be informed of the incident, as is procedure when a person dies who has been in recent contact with the police.
“No further details will be released at this time.”
> The IPCC has confirmed to the Citizen that their investigators have attended the scene of the incident in Midland Road, the hospital the man was taken to, and the post-incident procedures at Luton Police Station where officers involved provided their initial accounts.
The evidence gathered so far indicates the man was detained by police officers at around 12.35pm. The ambulance service was called shortly after and the man was taken to Bedford Hospital where he was pronounced deceased at 1.17pm.
A post-mortem is due to take place today. The man has not been formally identified.
IPCC investigators have been provided with brief accounts of the incident by the officers who were at the scene. CCTV has been recovered from the area and body worn video, activated by two of the officers during the incident, has been downloaded and secured. A number of independent eye witnesses have been identified and will be interviewed in coming days.
IPCC commissioner Mary Cunneen said: “My thoughts are with this man’s family and friends at this time and I can assure them, and the local community, that we will carry out a thorough investigation of the circumstances surrounding his death.
“This incident occurred shortly after midday near the junction of Midland Road and Battison Street, close to Bedford town centre. We would appeal for anyone who witnessed the event to contact our investigators to assist us in building the picture of what happened that day.”
Witnesses are asked to contact the IPCC incident enquiry line on 0800 0969 070 or email firstname.lastname@example.org
Any witnesses to the incident are asked to contact investigators on 08000969070.