Police said the driver, identified as Vicente Martinez, struck two adults and four children in two separate crashes seconds apart on Saturday.
Martinez's family said he may have suffered a diabetic emergency during the crash.
Police say Martinez first struck two adults and two children in a parking lot in front of a Ross department store.
Seconds later, he struck two more children in front of Target, then swerved and hit two parked vehicles, one of which belonged to Paul Ruhl, who had just parked his white 4 door sedan in a handicapped parking space in front of Target.
"I look around and then the truck was on top of me. Then the little girl hit my windshield and was on the other side of my car and the other little girl-we thought may have been pinned underneath the truck but she was not," Ruhl told CBS DFW.
Before he got out his vehicle, Ruhl saw Martinez get out of his truck.
"When he opened his door, he had to walk across my hood to get out his truck and when he opened the door, he looked dazed," Ruhl told the station.
A 7-year -old girl was airlifted to Cook Children's Hospital, where she was pronounced dead. Another child remains there with serious, but non-life threatening injuries.
The other four victims were transported to Harris Methodist Hospital with non-life threatening injures.
Martinez was also transported to Harris Methodist hospital for evaluation.
Police are awaiting the results of his evaluation to determine if charges will be filed.