Police believed Sydney siege guman was a "human bomb".

More details have been revealed about the strategy behind the raid that ended the Sydney siege in December.

Senior police sources have told the Sunday Telegraph that the first police officers who stormed the Lindt Cafe believed that Man Haron Monis had a bomb strapped to his back that was ready to detonate.

The heavily armed officers of the State Protection Group, “knew as soon the hostage was shot … that they would be going through that door,” a senior police source said.

“The team who went through the doors still thought there were bombs (inside). They were more worried about the backpack than the gun.”

After the gunman was neutralised, the attention of police turned to the backpack. The bomb squad was sent in, but the backpack contained “no explosives or bombs, despite the wires that had been seen protruding and his repeated threats to the hostages”.

The siege, which lasted some 17 hours, was a tense period of negotiation for specialist officers of the State Protection Group who were following standard operating procedures to contain and negotiate.

However, when cafe manager Tori Johnson was shot by the gunman direct orders were given to proceed with no hesitation. The SPG team carried out a “textbook entry” as they threw aside fears for personal safety and focused on getting the remaining hostages to safety. At that point, several hostages had already escaped the premises.

The country mourns Sydney siege victim Tori Johnson.

For more details:

These are the brave hostages of the Sydney siege.

What happened today: Sydney cafe under siege.

It’s over: Siege in Sydney’s Martin Place ends in shoot-out.