Ben Gallardo and his wife of four months, Susan, planned to have a large wedding ceremony at a Catholic church next week while he was home on leave from his duties as a naval corpsman at Camp Lejeune in North Carolina. The two were married by a justice of the peace in February.

But yesterday afternoon Gallardo, 27, sat in the living room of his in-laws' home in Damascus, attempting to grasp the fact that only hours earlier his wife had been killed in a car accident that also claimed the lives of two of her siblings.

Susan Gallardo, 19, Rodrigo Cruz, 24, and Enrico Engelbrecht, 23, were killed when their 1984 Chevrolet Cavalier collided with a Montgomery County school bus less than a quarter of a mile from their home. Carolina Engelbrecht, 20, a fourth passenger in the car, was critically injured and is at Suburban Hospital. Blanche Jeffers, 56, the driver of the bus, which was empty, was listed in stable condition last night at Montgomery General Hospital.

Montgomery County police spokesman Cpl. Phillip Caswell said that members of the Engelbrecht family were traveling west on Bloom Drive around 6:30 a.m. when the driver of the car, Enrico Engelbrecht, tried to make a left turn onto Rte. 27 going south.

The school bus, which was traveling north on Rte. 27, struck the car after Engelbrecht failed to grant the right of way, Caswell said. Police said they had not determined whether any of those involved were wearing seat belts, or at what speed the car and bus were traveling.

The accident caused southbound traffic from Damascus to be rerouted to Rte. 124 during the morning rush hour.

Although Caswell said he knew of no other fatal accidents at that intersection, one neighbor said it had been the scene of several accidents, including one in which she was involved. An embankment at Rte. 27 and Bloom Drive obstructs the vision of a driver trying to turn off Bloom as Engelbrecht was doing, the neighbor said.

Gallardo said that his wife and her siblings, who all lived at home, were on their way to work at Denro Laboratories, an engineering firm in Rockville, when the accident occured.

"I was asleep when they left and I didn't find out until two police came to the house around seven while I was watching TV," Gallardo said.

Holding back tears, he would say little about his wife except that she was "very sweet."

All the victims "were very friendly, especially Susan; she was very outgoing," Anthony Santiago, a family friend, said yesterday as he sat with Gallardo awaiting the arrival of friends from Virginia.

The victims' parents were in Alaska, where the father is a chief petty officer in the Navy, at the time of the accident. They were expected to return home last night, Gallardo said.