Thirty minutes before he was shot dead by gunman Man Haron Monis, Lindt cafe manager Tori Johnson sent an ominous text to his loved ones.

"He's increasing agitated ... walks around when he hears a noise outside with a hostage in front of him ... wants to release one person out of good faith - tell police," the text, sent at 1.43am on December 16, 2014, read.

The message was conveyed to police 10 minutes later, but Assistant Commissioner Mark Jenkins, who was in command of the siege at the time, says he was never made aware of it.