GANGLAND killer Carl Williams was left for dead for more than 20 minutes after he was attacked in the day room of the Acacia unit of Barwon Prison, despite the assault being captured on several security cameras.And Victoria’s Office of Police Integrity will join the investigation after allegations that corrupt police or former police are implicated in his death.Prison security footage shows that Williams was attacked from behind on Monday, then dragged about a metre to his cell and dumped inside. The alleged attacker then shut the door of the cell, leaving his victim fatally wounded.He used a towel to cover a pool of blood in the day room.After more than 20 minutes the alleged killer, who cannot be named for legal reasons, and a second inmate, ”Little Tommy” Ivanovic, notified staff that they might like to check on the welfare of Williams. Prison officers found him dead in his cell.Closed circuit cameras show one inmate detaching the reinforced seat support from an exercise bike in the day room and waiting until Williams was vulnerable. He was sitting at a table reading a newspaper when he was attacked. The footage shows he was struck in the head at least eight times.The attack took less than 10 seconds. ”He didn’t have a chance,” a prison source said.Police said there was no indication of any tension in the hours before the attack, although one prison source said there had been some bickering.The cameras are usually monitored but at the moment Williams was assaulted they were not because a prison officer was performing other duties. It is not known if the alleged killer knew the cameras were not being monitored. A former inmate who is suspected of organising at least one previous murder is under investigation over possible connections to the Williams hit.Police have established a financial link between the outside suspect and Ivanovic – one of two inmates present when Williams was attacked.Ivanovic and the accused killer have been interviewed by homicide squad detectives. Both refused to answer questions.Ivanovic has been listed as a prosecution witness against Paul Dale, the former drug squad detective charged with the mur-der of police informer Terence Hodson, who was shot dead with his wife, Christine, in their Melbourne home in May 2004.Hodson had agreed to give evidence against Dale and Detective Senior Constable David Miechel over an attempt to steal $1.3 million of drugs. Miechel was jailed but the case against Dale collapsed. Dale is accused of organising the murder of Hodson to prevent him testifying.Part of Ivanovic’s statement was leaked to the mainstream prison system. An inquiry failed to find the source of the leak.The Chief Commissioner of Victoria Police, Simon Overland, said police were confident they could establish how Williams was killed but would need to investigate why he was attacked.It could have been the result of a jailhouse spat or might have been organised by an unknown third party. He said Deputy Commissioner Ken Jones would oversee the investigation.Williams had been sentenced to life with a minimum of 35 years. He was a key figure in the Melbourne underworld’s vicious gangland war.Mr Overland said there was nothing to suggest his killing would spark further murders as most of Williams’s allies were either dead or in jail.Williams was allowed to associate with only two selected inmates because of fears for his safety.The unit can house 10 inmates but only three were in the section on the day.The director of the Office of Police Integrity, Michael Strong, said his office would have oversight and review of the police investigation of Williams’s death.Mr Strong said he made this decision after speaking to the Deputy Commissioner and the State Coroner, Judge Jennifer Coate.