FORT WORTH -- A 27-year-old mechanic was critically burned from his waist up Thursday after a fire at a west Fort Worth auto shop, a fire official said.Clifton Atkins suffered second- and third-degree burns in the blaze at Complete Auto Repair at White Settlement Road and Roberts Cut Off, authorities said."I heard the sound of tools and then I heard screaming," said Kari Scarbro, a dog groomer who works next door. "It was awful; he was really burned."Atkins was listed in critical condition Thursday afternoon at Parkland Memorial Hospital in Dallas, a hospital spokeswoman said.The fire was reported at 9:52 a.m., said Lt. Kent Worley, a fire spokesman. Atkins was working on a car's fuel pump in an "open air workspace" when witnesses heard an explosion."His brother came out after hearing the commotion and was able to pull him away and get him on the ground and get the fire out," Worley said. "But at that point he had already received extensive burns."The car he was working on was destroyed, and several other cars were damaged, Worley said. The shop's back wall was also damaged. Fire investigators estimated the damage at about $45,000.A helicopter ambulance took Atkins to the Dallas hospital.Investigators were still trying to figure out how the fire started, Worley said."It all happened quickly," he said. "Obviously something triggered an explosion or a flash fire."Employees at neighboring businesses stood on the sidewalk and watched as Atkins was loaded into the helicopter. Scarbro said that after the explosion she ran to the auto shop and saw Atkins' burns.He was conscious and possibly in shock because "he was just sitting there," she said."I know him pretty good so I'm just praying for him," she said. "He's going to have a long road."