"I just walked out of the doctor’s office and turned my head and just saw all this fire and smoke. It’s just incredible, really tragic,” onlooker Bob Prell said.

"It looks like the fire started [toward the back], and it just spread all across the building," onlooker Gerson Guerra said.

It took 50 fire units to get the fire under control. Although the blaze is still under investigation, initial reports indicate that a maintenance worker trying to fix a hose on a grill saw a flame leap up setting cooking grease ablaze.

"Unfortunately, with this structure, it is hard to get into the attic space because of the metal roof that they have," said Lt. Mario Hernandez of the Fire Marshal’s office.

The famous orange and white A-shaped roof Whataburger is known for today became its tragic flaw. The fire hit the attic space and firefighters had to spend extra time cutting through the metal to get to the fire.

"For the actual damage to structure it's pretty bad," Guerra said.

Because of the unique roof, firefighters were forced to evacuate and only work on the fire from the outside.

"I saw massive smoke and saw a lot of flame coming out of the top of the roof. I just couldn't believe it," Guerra said.

In just minutes, an estimated $100,000 worth of damage was done.