It sounded horrible. A man walking out of an Alexandria area grocery Thursday night was accosted by robbers, then set on fire when he didn't turn over any money. A friend said she doused him with water, then drove him to the hospital.

To police it sounded fishy. And by yesterday afternoon, Fairfax County robbery investigators believed that they had unraveled a hoax after the burn victim's friend reported her car as stolen. Police charged the friend with filing a false police report on the stolen car claim. The man has not been charged, said police, who are still investigating.

The man and woman appeared at Inova Mount Vernon Hospital about 11:30 p.m. Thursday. They reported that the man, a 31-year-old District resident, was walking out of the Shoppers Food Warehouse in the Penn Daw Plaza Shopping Center on North Kings Highway when he was confronted by two men demanding money.

The District man reported that when he denied having money, the men sprayed him with a flammable liquid and ignited it. His friend, Reyna O. Reyes, 34, of the Alexandria area of Fairfax, said she walked out of the store, saw the man struggling to quell the fire, and doused him with water.

Police were summoned to the hospital, where Reyes and the man apparently related their tale. The man was then taken by helicopter to Washington Hospital Center's burn unit with burns to his upper body. The burn victim did not have life-threatening injuries, police said. His condition was not available yesterday.

Investigators from both the Fairfax fire marshal's office and the police robbery section plunged into the case. A public appeal was made for witnesses to the fiery attack to come forward. Investigators swarmed the Penn Daw area.

But when Reyes called police again yesterday to report that her 1994 Nissan Quest had been stolen, robbery detectives questioned her more closely. This time, another story emerged, police said.

Police now believe that Reyes and the man were not supposed to be together, for reasons police would not discuss yesterday. On Thursday night, the man was working on her car in Prince George's County and burned himself, Officer Bud Walker said.

Rather than report the accident and risk being seen together in Maryland, the two drove to Fairfax and concocted a story, Fairfax police said. But when Reyes called police again yesterday to report a stolen car, investigators dug deeper and uncovered the hoax, Walker said.

Police said they would identify the man after they have charged him.

"We've certainly had cases of false police reports," Walker said. "But we've rarely had anything this elaborate."