Businessman Found Shot in His Car : Crime: Police say Gary Sinkus, who lived in Whittier and was co-owner of a Diamond Bar contracting firm, appears to have been a victim of a robbery.

Los Angeles County sheriff’s detectives are asking for the public’s help in solving the death of a businessman whose body was found Sunday afternoon in the trunk of his car.

Gary Sinkus, 40, of Whittier was found inside his white 1991 Mercedes-Benz outside a Rowland Heights Motel 6 at about 12:30 p.m., said Sheriff’s Deputy Mark Bailey.

Sinkus had been shot once in the head and appeared to have been the victim of a robbery, Bailey said.

Homicide Lt. Derry Benedict said Sinkus’ wallet had been stolen and that his credit cards were missing. Benedict would not say whether Sinkus’ credit cards had been used.

The coroner’s office is trying to determine when Sinkus died and how long his body had been in the trunk of his car, Benedict said.

“It is very strange,” Benedict said. “At this point, we’re grasping at straws.”

Sinkus, co-owner of Tecnicad Inc., a Diamond Bar general contracting firm, had called his family about 4:30 p.m. Friday to tell them he would be home for dinner, Bailey said.

At about 4 a.m. Saturday, when Sinkus had not returned home, family members called the police, Bailey said. Later that morning, the family filed a missing persons report with the Whittier Police Department.

Sinkus’ family conducted their own search and found his car parked in front of the motel early Sunday afternoon, Bailey said.

Emmett Gossen, spokesman for the Motel 6 chain, said that Sinkus’ car was not registered to any guests at the motel. A manager had remembered seeing the car parked in the motel lot when he made his rounds at about 9 p.m. Saturday, Gossen said.

Sinkus also co-owned Professional Physical Therapy in Whittier with his wife, Valerie.

Anyone with information on Sinkus’ death may call homicide detectives at (213) 890-5500.