HOUSTON -

Firefighters rushed to save four people trapped inside an apartment that was engulfed in smoke and flames.

The fire broke out around 4 a.m. Wednesday at an apartment on Walnut Bend and Richmond in southwest Houston.

When fire crews arrived, officials said they had to extend a ladder to the upstairs window to help people escape.

Investigators said the fire was very likely intentionally set.

"It appears some type of incendiary device thrown into the apartment. This fire will be under investigation." said Jay Evans with the Houston Fire Department.

Abria Bethely said he and his friends and family were playing video games when they heard a loud explosion and saw flames.

"Looks like a fireball, like something came through and came through the window -- gas or something. It went everywhere," said Behely.

Michael Bethely said this fire is just the latest violent act from someone who is targeting his family. He said his cousin received threatening text messages from the person only moments before the fire started.

"I guess they were just being evil. I guess you got to ask that person," said Michael Bethely.

Several days ago, officials said someone set fire to a car belonging to somebody who lives in the same apartment unit. Arson investigators are checking to see if the two incidents are related.

While the investigation continues, the Bethely family is trying to salvage what they can out of the apartment.

Anyone with information is asked to call Crime Stoppers at 713-222-TIPS.