The man's body was discovered around 4 a.m. in the parking lot of the Quick Trip on Bryant Irving Road, south of Interstate 20 in Fort Worth.
Someone noticed he was not moving inside the cab of his Groendyke Transport vehicle, even though all his gasoline hoses were in place.
Police said he died from a gunshot wound that did not appear to be self-inflicted.
"Our thoughts and prayers go out to the loved ones and family members of our driver involved in this morning's incident. We are shocked and saddened by this tragedy," said Groendyke spokesman Chris Pape.
The man was a local night shift driver for Groendyke and had worked for the company for about one year.
So far there have been no arrests and no information about a suspect was released.
Fort Worth detectives are checking surveillance video to see if it shows anything, and they're talking to witnesses.
The victim's fellow drivers are trying to resume operations with a heavy heart and a lot of questions.
"People that work here are family, and the team of people we have here in Fort Worth, this is hard to take," said Gregory Hodges, President of Groendyke.
When detectives arrived on scene, they found the driver dead from a gunshot wound. It was immediately ruled a homicide.
"We believe it happened between 1:30 and 2:30 in the morning, so we are asking for the public's assistance if you were in the area and if you saw anything suspicious or anything at all," said Cpl. Tracey Knight with the Fort Worth Police Department.
What's unclear is whether the death stemmed from a robbery, a random act, or someone who knew the victim.