A routine traffic stop in Santa Rosa yielded more than a police officer was bargaining for when the driver appeared to be in a "Jason" mask.

Just before 10 p.m. Saturday, the Santa Rosa Police Department said an officer noticed a Gold Toyota Camry without any headlights or taillights.

After pulling the car over, police said the driver was found to be wearing a "Jason" mask,

According to police, the officer described the driver as seeming to be "nervous" and noticed he was "sweating profusely."

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Jason mask and rifle

A traffic stop led to a driver wearing a "Jason" mask being arrested, according to the Santa Rosa Police Department.   (Santa Rosa Police Department)

The Santa Rosa police officer then located an AR-15-style rifle slightly concealed by a blanket in the back seat.

Police said the firearm, which was unloaded, was an unregistered assault weapon and is not legal to possess. 

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Santa Rosa law enforcement vehicles

Santa Rosa Police arrest a driver who was wearing a "Jason" mask and illegal assault rifle.  (Santa Rosa Police )

The driver, identified as Adonay Efriem, 27, of Santa Rosa, was placed under arrest without incident. 

Efriem was booked into the Sonoma County Main Adult Detention Facility for possession of an assault weapon.

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Masked Crook

Crook with a mask covering his face (Cyberguy.com)

According to the police department, the Santa Rosa Police Department Special Enforcement Team was developed to address the rise in illegal firearm possession and the rise in gun violence in the City of Santa Rosa.

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"The Santa Rosa Police Department is committed to making the City of Santa Rosa a safe place to live, work, and play," the department said in a statement. 

Fox News Digital reached out to the Santa Rosa Police Department for comment.