It happened just after 4am at the Cancun apartment complex on Wirt and Amelia.
"I heard people screaming. They came knocking to my door," said resident Mario Lagunas.
Neighbors in and around the burning three-story building say they rushed out to safety moments after the alarms began sounding. The fire got real intense.
"I saw this man jumping out of the window. He broke the glass and he was hanging. He tried to jump out," said Lagunas.
As dozens of emergency workers raced to the scene, investigators say a complete wall of fire surrounded the place, forcing them to request additional help.
"At least four apartments fully involved, and they were extending, the flames were extending over to the second building," said HFD spokesman Jay Evans.
Firefighters say one side of the building began to collapse. A tenant trying to escape fell through a staircase and injured his back. A firefighter also suffered back injuries when he fell through a structurally unsound roof. Another Houston firefighter suffered a hand injury.
One family who lived in the now-burned out building says the fire started after a boiler overheated, causing flames to shoot out. They say they had complained about the boiler to management last week.
"We had reported it to the office, and for them not to do anything, like, it kind of sucks," said resident Jennifer Huente.
Now arson investigators are looking into the official cause of the fire. The Red Cross is helping those displaced residents.