The CHP San Francisco Division said investigators were called around 11:40 a.m. on eastbound Interstate 80, west of Treasure Island.
The call was for a fender bender-turned carjacking. The suspect was involved in that initial two-car collision.
"Exited his vehicle and then initially got into a confrontation with the driver of the other vehicle, trying to steal that car," said Lt. Ross Ingels from CHP San Francisco. "Was unsuccessful stealing that vehicle, however he was able to brandish a firearm and steal another vehicle from a passing motorist."
Authorities said a white Chevy Colorado pickup truck with the license plate number 95222P2 was taken at gunpoint.
After the vehicle was taken, the Chevy driver continued eastbound on Interstate 80, toward Oakland. No one was injured in the initial accident or subsequent carjacking, officials said.
Video shot shortly after the incident and posted to the Citizen app shows the CHP on scene and three lanes of traffic on the lower deck of the bridge, closed for that investigation that resulted in a major traffic backup.
Now CHP say they're working with neighboring agencies and putting out the word to look for the stolen Colorado and the man who took it. "Be on the lookout for that vehicle, we do consider that suspect armed and dangerous," said Ingels. "So, if you do see the vehicle, please call 911 and let law enforcement respond to where you are."
The suspect is described as a possible Caucasian or Hispanic man in his mid-30s.
The incident caused a massive traffic backup on San Francisco highways and the Bay Bridge.
The vehicle the suspect was initially driving that was involved in the collision on the bridge is being processed for fingerprints and other evidence that may lead them to their suspect.