Rudy Ray Rockett died of multiple gunshot wounds during a car trip with his stepson, Gregory A. Roy, said Niagara County District Attorney Caroline A. Wojtaszek on Friday.
What led to the April 29 shooting is unknown because Roy has refused to talk to authorities, said Niagara County Sheriff James R. Voutour.
Rockett's body was found May 19 in a Cattaraugus County ravine.
Roy was arraigned on a murder charge on Friday.
Roy, who was already in custody on another charge, initially refused to attend a scheduled arraignment in Niagara County Court. So Niagara County Judge Matthew J. Murphy III issued a so-called "drag order," allowing corrections officers to use whatever force necessary to bring Roy to court from the Niagara County Jail.
He arrived in court about 45 minutes later. He pleaded not guilty to the murder charge and was remanded without bail.
He faces second-degree murder and criminal possession of a weapon charges in connection with the April 29 death of Rudy Ray Rockett, 64, of Redondo Beach, Calif.
Roy's home address is that of a vacation home in Porter near Lake Ontario owned by Rockett and his wife Elizabeth Rockett, Roy's mother.
Roy was supposed to drive Rockett to Buffalo Niagara International Airport April 29 so Rockett could fly back to California. Rockett didn't board the flight, however, and his wife reported him missing.
During the trip, Roy car took an unusual route in Niagara County, not directly to the airport, Voutour said. The shooting happened during that trip. Because of the unusual route, the victim probably knew they were not headed to the airport, the sheriff said.
Roy was arrested the next day on a weapons possession charge after police found an unregistered 9mm handgun in the glove compartment of his mother's 2006 Saab.
Police sources said they also found a substantial amount of blood on the passenger side door.
Roy was arraigned in Porter Town Court on the gun charge, but the case was delayed when Assistant Public Defender A. Joseph Catalano asked for a psychiatric examination of Roy. Two doctors interviewed him and concluded he is mentally competent to stand trial.
Friday, Assistant District Attorney Doreen M. Hoffmann renewed her request for a DNA sample from Roy to be compared to genetic material found on the gun.
After a tip from a citizen, Rockett's body was found by an Erie County Sheriff's Office cadaver dog in East Otto State Forest, where it was covered with tree limbs but had not been buried. Dental records were sent from California to enable the Erie County Medical Examiner's Office to positively identify the partially decomposed corpse.