"She immediately (screamed), 'I've been shot. I've been shot.' She took off running out the door," her son-in-law Bobby Cook told Dallas-Fort Worth television station KTVT.
The 62-year-old woman, whose name was not released by authorities, was taken to a nearby hospital with a "significant wound" and was listed in stable condition, police Lt. Paul Henderson said Monday.
The bullet is believed to be a rifle round and appears to have been fired from a long distance because it penetrated the roof at a slight angle, Henderson said.
He said he did not have information on whether investigators had any suspects.
Some 40,000 fans in about 10,000 to 10,500 recreational vehicles camped at Texas Motor Speedway for the weekend's races, said TMS spokesman Mike Zizzo, who declined to comment on the shooting.
The speedway does not release attendance figures for any races at its nearly 160,000-seat track.
Slideshow archive | ABC13 wireless | Headlines at a glance