Bobby Davis and Jack Twinning were career criminals—Twinning had spent time in eight federal prisons since the age of sixteen, including a stint at Alcatraz—and they were heading to Los Angeles with robbery on their minds when CHP units began following their vehicle after a reported incident minutes earlier. When Frago and Gore approached the car, Davis and Twinning initially cooperated. Then they opened fire. Both officers were killed before they could draw their weapons effectively. Officers Alleyn and Pence arrived moments later, engaged in a gunfight, and were both fatally wounded. A civilian bystander attempted to help using a recovered weapon but ran out of ammunition. A third patrol car arrived; the perpetrators exchanged shots and fled. The entire encounter lasted under thirty minutes.

George Michael Alleyn was 24 years old. Walter Carroll Frago was 23. Roger Davis Gore was 23. James E. Pence Jr. was 24. All four had been married. Among them they had seven children. All had joined the California Highway Patrol within the previous two years, young men at the beginning of careers they believed in. Twinning was captured three miles from the scene after taking a homeowner hostage; he released the hostage and killed himself with a stolen shotgun when deputies moved in. Davis stole a car and was apprehended by police. He was convicted in 1972 and sentenced to death, later commuted to life without parole. He died by suicide in prison in 2009.

Law enforcement agencies across the country studied the Newhall incident the way aviation authorities study plane crashes: looking for every decision that went wrong, every gap in training or procedure that contributed to the outcome. The analysis was unflinching. Officers Frago and Gore had approached the vehicle without waiting for backup, a tactical error. The three officers who fired their handguns had been using .357 Magnum ammunition but had only trained with .38 Special, which handles differently. Officer Pence appeared to have emptied his brass casings before reloading—a habit from range practice that cost precious seconds in a real gunfight. The CHP became the first major state police department to issue speedloaders for revolvers. Firearms training was standardized across the department. The procedures for high-risk stops were rewritten.

In 2006, the California legislature designated a stretch of Interstate 5 between Rye Canyon Road and Magic Mountain Parkway as the "California Highway Patrol Officers James E. Pence, Jr., Roger D. Gore, Walter C. Frago, and George M. Alleyn Memorial Highway." A dedication ceremony was held in 2008, on the 38th anniversary of the incident, attended by the civilian bystander who had tried to help that night, then 69 years old. The four names on the highway sign are those of young men whose deaths made American policing measurably safer—a cold comfort, but a real one.