Five sheriff’s deputies from Southern California and three National Guardsmen were killed when the helicopter they were flying in a joint drug interdiction mission snagged on a power line and exploded into a hillside in western Imperial County, authorities said.

The accident occurred Monday, Oct. 24, about 9:30 p.m., approximately 63 miles east of San Diego on what was described as a training flight on the first night of an unpublicized anti-drug surveillance program called Operation Border Ranger. The National Guard UH-1H Huey helicopter crashed when it tried to make a pass through an isolated canyon to close in on a parked car thought to belong to drug smugglers, a National Guard spokesman stated.

Killed in the crash were five deputies from a consortium of six Southern California sheriff’s departments that sponsored Operation Border Ranger, an anti-drug smuggling program that was quietly organized earlier this year. The three dead guardsmen were stationed with the 140th Aviation Unit at the Los Alamitos Armed Forces Reserve Center in Orange County.

October 24 was the first day that sheriff’s deputies and the guard had employed the helicopters in the effort, and then maneuvers during the day were performed without incident, Imperial County sheriff’s Lt. Kenneth Koon said.

In all, the guard sent three helicopters and 27 personnel to Imperial County, officials said.

The dead deputies were identified as Roy A. Chester, 41, of La Verne, and James D. McSweeney, 43, of Huntington Beach, both 12-year Los Angeles County Sheriff’s veterans; Sgt. Richard G. Romero, 39, El Centro, a 14-year veteran in Imperial County; Mark Steven Tonkin, 31, Chino, a seven-year member of the Orange County Sheriff’s Department; and Investigator Michael David Davis, 34, Indio, a nine-year veteran Riverside County deputy. San Diego and San Bernardino county sheriff’s departments, the other participants in the program, had no one on board.

The deputies who died were all experienced narcotics officers.

Chester, who is survived by his wife, Marilyn, a 19-year-old daughter and twin 17-year-old sons, joined the narcotics detail in March 1984, and received numerous citations and commendations.

McSweeney, divorced and with no children, was once shot in the arm and chest while apprehending an armed narcotics suspect.

Davis was awarded the Medal of Valor in 1987 for the rescue of a fellow officer from a brush fire. His wife, Sandy, and four children, ranging in age from 9 to 17 survive him.

Romero was in the same 1966 Calexico High School graduating class as slain Drug Enforcement Administration Agent Enrique Camarena.

“At the baccalaureate they said some of you in the crowd will probably go places, some will die, some will end up going crazy . . . It has come to pass,” said Tony Ramos, a member of the same class and now a deputy Imperial County probation officer.

Romero, a 14-year veteran, was not scheduled to be on the flight but pulled rank and bumped another deputy to get a seat on the ill-fated training mission, Koon said.