The Orlando killer claimed to have laid explosives outside the Pulse nightclub and threatened to put suicide vests on hostages, newly released FBI tapes from the night of the shootings reveal.
Partial transcripts released today show that gunman Omar Mateen claimed to have explosives like those used in the Paris terrorist attacks last November during multiple contacts with police in a three-hour stand off.
He repeatedly pledged allegiance to Islamic State and demanded that the US stop bombing Syria and Iraq in "chilling, calm and deliberate" conversations during the attack which killed 49 people.
The written transcripts show that Mateen called the 9/11 emergency line just after 2am and told the operator "I’m in Orlando and I did the shootings."
Specialist negotiators managed to speak with him three times, between around 2.45 and 3.30am, as he holed up in the club toilets with a group of hostages.
In the calls Mateen claimed to have a suicide vest like they "used in France" and also claimed to have planted bombs outside the building.
The FBI's timeline also shows that victims being helped out of the club at 4.30am said Mateen had threatened to put suicide vests on four hostages being held in the club toilets within 15 minutes.
It later emerged that the killer did not have any explosives. However, the threats may partially explain why it took so long for police to break the stand off.
Authorities today said they had taken the decision not to release audio from the Mateen's calls out of respect for victims.
The FBI said they were still working on what attorney Lee Bentley today described as "the most significant terrorist attack since 9/11".
They have stressed that Mateen did not appear to have been directed by anyone else but was rather radicalised online.