CONCORD, CALIF. -- Angry demonstrators returned yesterday to the Concord Naval Weapons Station where Vietnam war veteran S. Brian Willson, protesting U.S. arms shipments to Central America, lost both legs Tuesday as he knelt in front of an oncoming munitions train.

The protesters, in a news conference, denounced the Navy for failing to stop the train.

Capt. Lonnie Cagle, commander of the base 45 miles east of San Francisco, said the train engineer "was under no orders" to proceed through the demonstrators without stopping. Public affairs officer Dan Tikalsky said the train crew had been instructed to stop if anyone was on the tracks.

Several demonstrators said the train seemed to accelerate as it approached the protesters at a speed of at least 10 to 15 mph. Navy officials said a preliminary investigation showed that the civilian engineer was moving at 5 mph and had applied the brakes.

Willson's wife of 11 days, Holly Rauen, quoted her husband as saying, "Well, I'm a real peace agitator."

Willson, 47, an activist who last September participated in a 47-day fast on the Capitol steps, had been leading about 25 demonstrators. One leg was severed below the knee and surgeons amputated the other leg below the knee, said a spokeswoman for John Muir Hospital. Willson had a skull fracture and other injuries and was in serious condition.

Willson is a leader of the Veterans Peace Action Team, which has marched through combat areas in Nicaragua to protest U.S. support for the contras.