A 68-year-old Annandale man, in flames and screaming for help, came running out of the woods at a Fairfax County park yesterday, leaving police to investigate how he got to the park and how he was set on fire.

James Francis McNelis, who lives in the 4100 block of Breezewood Lane a half-block east of the park, was reported in critical condition last night at Washington Hospital Center with third-degree burns over most of his body, officials said.

Workers at Mason District Park said witnesses alerted them to the burning man about 3 p.m. Passersby had spotted him near a picnic area near the entrance on Columbia Pike.

The witnesses saw no one else in the area, and police said they did not yet know if McNelis had been abducted or if there was another explanation for what had happened.

"We may not even have a crime here," Lt. Amy Lubas said. "We're just calling it a suspicious event."

George Cook, lead crew chief for the park, said he rushed to the scene after a motorist told him that a man was in distress in the picnic area. When he arrived, McNelis was lying on top of a picnic table. Cook said he ran over with a fire extinguisher but the flames were already out.

"His entire body was burned. His clothes had burned off," Cook said. "He was conscious, saying how much pain he was in. We just comforted him."

Cook said that after a witness told him there was a fire in the nearby woods, he went into the trees and put out three small fires. He described one fire as "the length of a body." He said he also saw a gasoline can nearby.

Richard Maple, area manager for the park, said that he dialed 911 and that rescue workers arrived within four minutes. McNelis was stabilized and driven to a soccer field in the park, where a helicopter landed to take him to the burn unit at the hospital.

One of McNelis's neighbors on Breezewood Lane said yesterday that McNelis and his wife are very private and "very, very nice people." McNelis had been in the military, the neighbor said, and had served in Vietnam.

The neighbor, who declined to give her name, said that McNelis's daughter is scheduled to be married sometime this month.

Staff writer Josh White contributed to this report.