About 40 people were at the restaurant on Sunday when the explosion occurred.
One man was in a partitioned room on the second floor with five friends when the blast ripped through the realtor's office next door.
He said there was a loud pop, then all the lights went out and the ceiling came down.
Part of the floor collapsed, and the restaurant's outer wall was blown away.
The man said he thought it was an earthquake, and couldn't understand what was happening. He said he saw a parent trying to calm a frightened child.
Moments later, he heard a woman calling for help from the toilet on the second floor. He and his friends helped get her out.
By that time, firefighters had arrived and had begun rescuing customers using a ladder. No one was wearing shoes, as they had all been left on the first floor.
The man was waiting for his turn to go down the ladder. But a few minutes after the explosion, flames began spreading through the store.
The man said the heat became so intense that he jumped. Several others did the same.
He cut his feet on the debris strewn below, and the back of his jacket was charred.
The man said he could have died, and that he is still frightened of dark places. He said he's troubled because he cannot work because of his injury.