Pike River Coal chief executive Peter Whittall did not know that a fire was burning underground a day after the explosion now thought to have killed 29 miners.
An emotional Mr Whittall told the royal commission of inquiry he did not initially know film of the first blast existed.
Mr Whittall has been accused by the dead miners' families of giving them false hope.
Yesterday, he told the commission it was "extraordinary" he did not learn crucial facts about the mine explosion until the inquiry began.
Royal commissioner Stewart Bell questioned why someone as experienced as Mr Whittall had clung to the hope that there were survivors.
Struggling to compose himself, Mr Whittall said he had read with disbelief the evidence from every family, and could only read a couple a day because the views were so upsetting.
To say he was devastated by them would be an understatement, he said.
Many had accused him of giving false hope but he could not think of why he would do that.
If anyone's suffering was made worse by that, he was "absolutely sorry".
He had genuinely believed there was a chance that some men could have survived and "come back to us".
"I had a hope in myself and I shared that hope."
The commission watched film of a press conference the day after the disaster at which Mr Whittall suggested the 29 men could be sitting around "an open pipe waiting for someone to come in".
It was not until the following day that survivor Daniel Rockhouse told him the air pressure coming out of the vents was very low.
Mr Whittall said he did not know a camera was mounted at the portal, let alone that film of the blast existed, until November 21, two days after the explosion.
Several people on the site immediately after the blast said a fire was burning in the mine, but Mr Whittall said he had had "absolutely no knowledge of any of those opinions".
He was on site at Pike River when the second explosion happened, and had watched film of it "over and over again".
"It was devastating."
In halting, tearful testimony, Mr Whittall said he met police Superintendent Gary Knowles in the car park of the Greymouth Civic Centre as the families swarmed around.
"It was horrendous ... I knew the second explosion had occurred and they didn't know."
He felt sick, did not know what to say, and was overwhelmed.
Inside, 500 family members and friends and 60 or 70 police officers had gathered.
He told them Mines Rescue had been going to enter the mine, but people did not pick up on the past tense and started cheering and clapping.
He said in hindsight, there must have been a thousand better ways he could have delivered the message.
Back in the dock after a break to compose himself, Mr Whittall said he became aware of film of the first explosion only several days later.
And the first time he knew a fire was burning in the mine was after the fourth explosion.
Two mine managers and gas analysts had told the commission it was possibly methane burning, but Mr Whittall said no one had ever suggested to him, "until I sat in this court", that there was a raging fire.
- Greymouth Star