In less than five minutes, the four CHP officers were killed and another man was pistol-whipped in what was at the time the deadliest day in the history of California law enforcement.

[7][8] En route to Los Angeles, they noticed construction along the highway near Gorman and believed they could steal explosives there to commit a robbery.

At approximately 11:20 p.m. (UTC-8), Davis was driving northbound on Interstate 5 south of Gorman when he made an illegal U-turn across the highway median, nearly colliding with a southbound vehicle driven by Ivory Jack Tidwell (1925–2016), a serviceman en route to Port Hueneme with his wife, Viola Bernice White (1936–2019), as passenger.

[7][10] Several minutes later, CHP officers Walt Frago and Roger Gore, partners in the same 1969 Dodge Polara patrol car, spotted the red Pontiac near Castaic and began following the vehicle.

Officers James Pence and George Alleyn, partners in a second 1969 Polara patrol car, waited in nearby Valencia ready to back up Frago and Gore.

The suspect's vehicle exited the freeway at Henry Mayo Drive, near the present-day site of Six Flags Magic Mountain, and pulled into the parking lot of J's Coffee Shop, adjacent to a Standard gas station.

Obeying the officer's orders, Davis exited the driver's seat and walked to the front of the vehicle, where Gore proceeded to search him.

Meanwhile, Frago approached the other side of the car carrying a shotgun at "port arms" with the stock against his hip and the barrel pointed in the air.

[7][10] As Frago walked to the Pontiac, Twinning exited the passenger seat and opened fire with a Smith & Wesson Model 28 revolver.

Davis and Twinning immediately opened fire on them with their pistols, expending all their remaining rounds, and dove back into their own car for new weapons.

[9] Davis pulled out a sawed-off 12-gauge Western Field (re-branded Mossberg produced for the Montgomery Ward chain) pump-action shotgun, while Twinning grabbed a semi-automatic Colt M1911 .45 ACP caliber pistol.

Meanwhile, Alleyn emptied his Remington Model 870 shotgun at the Pontiac, firing the gun so fast he accidentally ejected a live round in the process.

After expending all his shotgun rounds, Alleyn opened fire on Davis with his Smith & Wesson Model 19 .357 Magnum revolver but did not make any hits.

Davis returned fire with his sawed-off shotgun, striking Alleyn with ten rounds of 00 buckshot and inflicting fatal injuries.

Hoag's wife, Betty, and their 17-year-old son, Jeff, escaped and called police, and soon the house was surrounded by deputies from the Los Angeles County Sheriff's Department.

As police, led by Los Angeles County Sheriff’s Sergeant Robert Lindblom, entered the residence, Twinning killed himself with Frago's shotgun.

Davis was found dead, aged 66, in his maximum-security single cell at Kern Valley State Prison, an apparent suicide, on August 16, 2009.

[16] A key mistake made by Gore and Frago, thought to be related to their inexperience, was proceeding to approach and search the suspects immediately after pulling them over.

Had they waited for Pence and Alleyn to arrive within a minute or so, it is possible Twinning and Davis would have surrendered or been overwhelmed by superior firepower when faced with 4-on-2 odds.

Frago had mistakenly approached the vehicle with his shotgun held diagonally in front of his body and Alleyn had ejected a live round.

[18] In the aftermath of the Newhall shooting, although this was not based on the actions of any officer involved in the incident, the CHP modified their training to eliminate the practice of "pocketing brass" on the range (the act of picking up spent cartridge cases before reloading with fresh rounds).

This was confirmed by CHP Chief John Anderson in his book The Newhall Incident: America's Worst Cop Massacre.

[19] California Senate Concurrent Resolution 93, introduced by Senator George Runner, designated Interstate 5 between the Rye Canyon Road overpass and Magic Mountain Parkway in Santa Clarita as the "California Highway Patrol Officers James E. Pence, Jr., Roger D. Gore, Walter C. Frago, and George M. Alleyn Memorial Highway" and was passed on August 11, 2006.