A gunman is holding up to 20 people hostage in complete darkness at a cafe in Sydney, Australia according to Sky News. Chilling footage emerged of a female hostage apparently trying to communicate with police by miming her throat being cut, while news channels have chosen not to broadcast a video of another hostage relaying the assailant’s demands. Witnesses described seeing the hostages looking “exhausted” and “absolutely petrified” – but as night fell and the siege entered its 11th hour the gunman turned off the lights, meaning people outside could no longer see in. Earlier, two Arabic flags similar to those used by Islamic State were seen inside the Lindt cafe in Martin Place, the city’s financial hub. Channel Ten has spoken to two hostages who say the gunman claims to have four bombs, two inside the cafe and two in the financial district. Police are investigating reports the assailant has used hostages’ social media accounts to demand a meeting with Australian Prime Minster Tony Abbott. It is now thought officers know the identity of the man, who appears to be carrying a pump-action shotgun and that he was previously known to the Sydney police. Some of the hostages have spoken to their families on mobile phones, while five, three male customers and two female staff, have managed to escape since the siege began more than 11 hours ago. Journalist Chris Reason, who has a view of the cafe from the Channel 7 building, said the gunman was “extremely agitated” when the hostages fled.