LONDON, England (CNN) -- A police officer has been interviewed under caution for manslaughter after tests on a man who died during G-20 protests in London, the UK police watchdog said Friday.
A video posted by the Guardian shows police shoving Ian Tomlinson to the ground. He later died of a heart attack.
Ian Tomlinson died on April 1 in the city's financial district as demonstrations took place against the G-20 summit being held in the city.
Several videos of the same incident -- one of which was shot by an American visitor -- show a police officer apparently pushing Tomlinson to the ground.
An initial autopsy said that Tomlinson's death had been caused by a heart attack. But a second autopsy, announced Friday, has revealed that he died from abdominal hemorrhage.
In a statement Friday the Independent Police Complaints Commission, which is investigating the incident, said: "Following the initial results of the second post-mortem [autopsy], a Metropolitan Police officer has been interviewed under caution for the offence of manslaughter as part of an ongoing inquiry into the death of Ian Tomlinson."
The new autopsy was undertaken on the instructions of the IPCC and Tomlinson's family. Watch video showing police allegedly shoving man »
Paul King, in a statement on behalf of Tomlinson's family Friday, said: "First we were told that there had been no contact with the police, then we were told that he died of a heart attack; now we know that he was violently assaulted by a police officer and died from internal bleeding.
"As time goes on we hope that the full truth about how Ian died will be made known".
In one of the videos, Tomlinson, who had his hands in his pockets, is shown walking away from police with his back to the officer who then pushes him.
Tomlinson was able to walk away from the scene of the push, but a few minutes later he died of what the initial autopsy said was a heart attack.
His family have said that he was not involved in the protests taking place in London's financial district at the time.
The City of London Coroners Court said in a statement Friday that pathologist Nat Cary, who conducted the second autopsy, accepted earlier findings that Tomlinson suffered from coronary atherosclerosis -- but that the nature and extent of the condition were unlikely to have contributed to his death.
The coroner's statement said that the findings of both autopsies was provisional and that both pathologists involved agreed on the need for further investigations and tests.
Jules Carey, solicitor for Tomlinson's family, said that "the video footage of the unprovoked and vicious assault on Ian by the police officer would easily justify charges of assault being brought against the officer.
"The findings of Dr. Nat Cary significantly increase the likelihood that the officer will now face the more serious charge of manslaughter."
He added Tomlinson's family had been aware of the findings of the second autopsy for a week but "had to endure the holding back of this information despite continuing reports in the press that Ian died of a heart attack."
Cary said the IPCC opposed the disclosure of Dr Cary's findings until they satisfied themselves that it would not prejudice their investigation of the officer, Carey said.
"It is of some comfort to the family that the record is now being put straight, but they hope that the IPCC investigation will be expedited and thorough, and that there will be a prompt referral to the CPS for charge."
In a statement the Metropolitan Police Service said that it wished to reiterate its sincere regret in relation to the death of Ian Tomlinson. "Our thoughts are with his family, and all those affected by this tragedy."
It added that it was unable to comment on the autopsy findings as the independent investigation by the IPCC was ongoing.