It happened early Tuesday morning in the 6500 block of Zaragoza near Baytown.
Deputy Roberto Martinez, who has 10 years of law enforcement experience, was nearby when he got the call around 3:20 a.m.
FULL VIDEO: See the deputy's heroism in action
"Just broke the window like I had to, that was the easiest thing to do. The front door was completely engulfed," said the deputy.
A family of five adults and two children - ages 7 months and 3 years old - live inside the home.
They all escaped through another window except grandmother Eloisa Martinez, who tells ABC13 Eyewitness News she got trapped in the darkness and thick smoke.
"I was scared, I was scared. I just didn't know how I was going to get out," she said.
The video captures the deputy's efforts to get to the grandmother, but he says a dresser blocked his way in.
"It had to be at least six feet tall because it was up there, it was probably covering the entire window," said the deputy.
"He broke the window and I had a cabinet there in the front, and so he pushed it over and I was able to crawl through and get to the window," said Eloisa.
Eloisa calls this deputy her godsend, telling us he saved her life.
"If he wouldn't have come when he did, I would probably be passed out on the ground, on the floor," she said.
Deputy Martinez says this was his first house fire rescue and declined to be called a "hero."
"I was just doing what I have to do. Anyone of us would have done it," he said.
He tells Eyewitness News he would do it all over again.
Both Deputy Martinez and Eloisa were treated and released from the hospital, where they got to meet again.
Eloisa's husband remains hospitalized for observation.
The Harris County Fire Marshal's Office is investigating the cause of the fire and have not determined why it started.
The family lost everything in the fire and have started a GoFundMe account to help buy items for the children. You can click here to donate.