But Mateen's ISIS pledge will not be released as

'to get as much information about this investigation out as possible'

Authorities will release redacted transcripts of his conversation with hostage negotiators on Monday

Mateen also referred to the Boston marathon bombers as his 'homeboys'

He pledged allegiance to ISIS and talked about his

Authorities are set to release transcripts of calls between Orlando shooter Omar Mateen and hostage negotiations during the worst mass shooting in US history.

Attorney General Loretta Lynch said the transcripts will reveal what the gunman discussed with the authorities during the terrorist attack at Pulse nightclub, Florida.

'He talked about his pledges of allegiance to a terrorist group,' she told WTAE. 'He talked about his motivations for why he was claiming at that time he was committing this horrific act.

'He talked about American policy in some ways,' Lynch added. He also mentioned his support for the terrorists behind the Boston bombings, FBI officials report.

Scroll down for video

Attorney General Loretta Lynch (right) said the Justice Department will release transcripts of calls between Orlando shooter Omar Mateen (left) and hostage negotiations during the worst mass shooting in US history

However, Mateen's pledge of allegiance to ISIS and support for the Boston bombers will not be released as not to 're-victimize' those who lived through the attack.

'We'll be releasing a partial transcript of the calls between the killer and the hostage negotiators so people can, in fact, see the type of interaction that was had there,' Lynch told ABC News.

'I say partial because we're not going to be, for example, broadcasting his pledges of allegiance. We are trying not to re-victimize those who went through that horror,' she added.

FBI Director James Comey said the shooter was involved in precisely three calls to a 911 dispatcher at approximately 2.30am on June 12.

FBI Director James Comey said the shooter was involved in precisely three calls to a 911 dispatcher at approximately 2.30am on June 12 (pictured is Pulse nightclub where Mateen shot dead 49 people)

'During the calls he said he was doing this for the leader of ISIS, who he named, and pledged loyalty to,' Comey said.

'But he also appeared to claim solidarity with the perpetrators of the Boston Marathon bombings and solidarity with the Florida man who died as a suicide bomber in Syria for Al-Nusra Front - a group in conflict with the so-called Islamic State.

'The Boston bombers and the suicide bomber from Florida were not inspired by ISIS, which adds a little bit to the confusion about his motives', Comey concluded.

Harold Shaw, special agent in charge of the FBI's Boston division, also said that during the calls Mateen made a reference to the Boston marathon bombers as his 'homeboys'.

Despite the reference, Shaw and other authorities have said the investigation has not uncovered any evidence of a relationship between the Tsarnaevs and Mateen.

The Attorney General said that authorities were releasing the redacted transcripts on Monday to try 'to get as much information about this investigation out as possible, and we want people to provide information that they have to us.'

She is planning to travel to Orlando on Tuesday to meet with victims and first responders.

Lynch told Fox News that federal investigators are in the middle of a 'very aggressive investigation' into the atrocity.

While she would not say whether investigators were planning to arrest Mateen's wife Noor Zahi Salman, amid claims she helped plot the terrorist attack, Lynch said the investigation was focused on re-tracing Mateen's steps during his final days.

The Attorney General said she is planning to travel to Orlando on Tuesday to meet with victims of the tragedy and first responders (pictured is people visiting a memorial to the tragedy in Orlando)

Lynch said the Justice Department was working to prevent any similar attacks happening in the future but said it was essential to 'keep our focus on the victims of this tragic crime'

'We are trying to re-create the days, the weeks, the months of this killer's life before this attack,' said Lynch. 'And we are also asking those people who had contact with him to come forward and give us that information as well.'

She said that more information will be released about the shooting as the investigation continued.

Mateen was previously the focus of two FBI investigations over his suspected terrorist links.

But both the 2013 and 2014 probes deemed him not to be a threat. He was therefore allowed to buy an AR-15 rifle and semiautomatic pistol which he used to kill 49 people at the Orlando nightclub, and injure more than 50 others.

Comey defended the agency's earlier investigation of the Orlando shooter saying that he didn't see anything his agents should have done differently during either of the earlier investigations.

Lynch said that 'we're looking into' how those probes were handled.

'This is an ongoing investigation. We are going back and scrubbing every contact we had with this killer,' she said. 'We're also asking people to come forward with the contacts they have had with this killer as well.'

Lynch said the Justice Department was working to prevent any similar attacks happening in the future but said it was essential to 'keep our focus on the victims of this tragic crime.'