5 Killed in Head-On Collision : Accident: A pickup truck slams into a packed van near Irvine Lake. Four of the dead were part of a family returning from a memorial Mass for a relative. Three others are injured.

Four members of a Walnut family caravaning home from a memorial Mass for a relative were killed Saturday afternoon when a pickup truck pulled onto busy Santiago Canyon Road near Irvine Lake and slammed head-on into their packed vehicle.

The driver of the pickup also was killed in the accident. The death toll could rise to six because one of the dead in the family’s vehicle was a 33-year-old pregnant woman, and the fetus did not survive. Senior Deputy Coroner Richard McAnally said an autopsy scheduled today will determine if the fetus--thought to be three months old--was developed enough to be listed as a fatality under California law.

Three other family members in the four-wheel-drive utility vehicle were injured.

“This is the worst crash we both have ever seen,” said Lisa Gadberry, an emergency medical technician who passed by the crash and stopped to render aid with a friend, Traci Muckelvane, 21. “There were bodies everywhere.”

As they consoled family members who had apparently been caravaning behind in two other vehicles, California Highway Patrol officers closed down Santiago Canyon Road, congested Saturday with hundreds of motorists.

Four people died at the scene: the driver of the family vehicle, Joe Cruz Norman Mendoza, 37; his 10-year-old daughter, whose name was not available; her 69-year-old maternal grandfather, Vicente Sanchez, and the pickup’s driver, Nahum Rincon, 40, of Ripon, in Central California, officials and family members said.

Mendoza’s pregnant wife, Maria Mendoza, died a few hours later at Western Regional Medical Center-Santa Ana.

Mary Sanchez, 67, the wife’s mother, suffered major injuries and was in surgery Saturday night at the Santa Ana hospital, where she was listed in critical condition. Two teen-age boys--Mendoza’s 16-year-old son, Joe Mendoza, and a 17-year-old nephew, Eric John--were in stable condition at Mission Hospital Regional Medical Center in Mission Viejo.

Other family members were in shock Saturday night when they arrived at the Santa Ana hospital to comfort the survivors. “It’s just like a dream. I still can’t believe it happened,” said Edwin Mendoza, 34, of Walnut, the brother of the elder Joe Mendoza. “It is a tragedy for the family.”

He said that he called family members, many of whom emigrated to the United States from the Philippines in the early 1970s, and told them of the tragedy.

The Mendoza family had just attended a memorial Mass at St. Michael’s Abbey in El Toro to commemorate the death a year ago of the elder Joe Mendoza’s brother, Fernando, who died of cancer at age 46, according to a nun at the abbey. The nun, who asked not to be identified, said Fernando Mendoza had made friends with a small convent of Rosarian Dominican nuns who share grounds at the Orange County abbey.

After the Mass, the family attended a picnic with the nuns, then headed north toward their Los Angeles County home on the rural and scenic Santiago Canyon Road. Two other carloads of relatives and friends apparently followed behind, a CHP spokesman said.

The pickup truck apparently had been on the shoulder of Santiago Canyon Road and was pulling back into the traffic lanes about 2 p.m. when it smashed into the northbound van, a 1991 red Toyota Four-Runner, in an unincorporated area, said Santa Ana CHP spokesman Mel Baker.

The crash closed Santiago Canyon from 2:30 p.m. to 7 p.m. Hundreds of motorists were prevented from going any farther south on Santiago Canyon Road than Chapman Avenue, unless they lived in the area. All traffic leaving Irvine Lake, which was crowded with fishing enthusiasts, was routed north into the city of Orange. Saturday was one of two “free fishing” days in California this year when no licenses are required for freshwater or ocean angling.

A member of the Rosarian Dominican Sisters at St. Michael’s Abbey said that the Mendoza family “was very religious,” and that the father and mother came to the convent every Saturday to say the Rosary.

The nun said one of the relatives brought news of the accident to the convent. “I was depressed and shocked,” she said. “I just prayed to God.”

Times staff writers Leslie Berkman and Carla Rivera contributed to this report.