The officer was working traffic enforcement in the area of Sebastopol Road and Burbank Avenue at around 4:10 p.m. when he spotted a gold 2002 Cadillac Escalade sport utility vehicle driving recklessly, police said.
He stopped the truck at the intersection of West and Sunset avenues.
The officer was not aware that motorists had called 911 and reported that occupants of the same type of vehicle had been brandishing a firearm at other drivers, police said.
The driver, 24-year-old Bonifacio Santos Alejandres of Santa Rosa, allegedly appeared evasive and gave the officer false identification, police said.
Alejandres allegedly refused to get out of the truck when the officer asked. The officer opened the door and started to escort Alejandres from the vehicle when he noticed that Alejandres' hand was suspiciously hidden behind his back, police said.
The officer saw that Alejandres allegedly had a loaded firearm in his hand that was pointed at the officer, according to police.
The officer struck Alejandres in the face and he dropped the weapon.
Emergency assistance was requested, and Alejandres was arrested on suspicion of assaulting a police officer with a firearm, assault with a deadly weapon, possession of controlled substances for sale, being armed with a firearm while in possession of controlled substances for sale, probation violation, and threatening an officer, police said.
The passenger of the truck, 30-year-old Joel Parra Orosco of Santa Rosa, was also arrested on suspicion of possession of controlled substances for sale and resisting arrest, police said.
Both men were booked in the Sonoma County Jail, and bail was set at $250,000 for Alejandres and $20,000 for Orosco.