Police are hunting a man who is in the US illegally and is accused of killing a California police officer on Wednesday.

Newman Police Department Corporal Ronil Singh, 33, was making a traffic stop early in the morning when he called 'shots fired' over his radio, according to the Stanislaus County Sheriff's Department.

Singh had pulled over a gray pickup truck in Newman, a small town 100 miles south of San Francisco, after noticing it had no license plate as part of a DUI investigation, Stanislaus County Sheriff Adam Christianson said on Thursday.

Signh fired back to defend himself, Christianson said.

Authorities have found the truck believed to belong to the suspect, who has not been named publicly, and remains at-large.

Police are hunting a man who is in the US illegally and is accused of killing a California police officer on Wednesday, after finding the truck believed to belong to the suspect (pictured)

Authorities released surveillance images of the suspected gunman sought in the shooting death of Newman Police Department Corporal Ronil Singh, 33

The vehicle, believed to have been the one stopped by Singh, was found in a garage in a mobile home park about 4 miles (6 kilometers) away from the scene of the shooting.

The silver, extended-cab Dodge Ram 1500 pickup was seen in the area at the time of the shooting, and had paper plates on the vehicle, which read 'AR Auto.'

Working off several tips from the public, the vehicle was discovered about 13 hours after the shooting at a River Road mobile home park just south of Azevedo Road, where law enforcement officers were serving a search warrant.

Police confirmed the pickup was the one believed to have been driven by the suspect.

Crime scene tape was seen inside the mobile home park, where several media outlets, including some from the Bay Area, Sacramento, Salinas and Fresno, converged late on Wednesday afternoon.

'There's lots of potential evidence,' a police spokesperson said. 'Fingerprints, DNA, gunshot residue and physical evidence. We'll be processing the truck to get any evidence to help in the prosecution.'

Police investigate the scene of a shooting that took the life of Newman Police Officer Singh

The unidentified suspect, who was pictured on CCTV entering a store shortly before the fatal shots were fired, remains at large.

Officer Singh was found with multiple bullet wounds, and was taken to a local hospital where he was pronounced dead.

The sheriff's office released surveillance footage stills of the suspect and the gray, extended cab Dodge Ram pickup truck found near the location of the shooting that is believed to be the gunman's vehicle.

The suspected gunman appears in the images in an unzipped hooded sweatshirt and gold chain while purchasing items in a store.

Ronil Singh is survived by his wife, Anamika, and a 5-month-old son, authorities said

Singh was a native of Fiji and the father of an infant son. He joined the Newman police force in 2011.

Earlier in his career, Singh worked as a deputy with the Merced County Sheriff's Department.

'He was living the American dream,' said Stanislaus County sheriff's Deputy Royjinder Singh, who is not related to the slain officer but knew him.

'He loved camping, loved hunting, loved fishing, loved his family,' the deputy said.

On his Facebook page, Singh posted pictures on Christmas Eve from a deep-sea fishing trip that produced a big haul of crabs and fish. The profile picture shows him smiling as he stands at a patrol car with a dog - the same photograph of the officer released by the Sheriff's Department.

The slain officer, who lived in Modesto, is survived by his wife, Anamika, their 5-month-old son, his parents and a brother.

Outgoing California Gov. Jerry Brown offered condolences to Singh's family and said flags at the Capitol would fly at half-staff in his honor.

'Our hearts are with the entire community of Newman and law enforcement officers across the state who risk their lives every day to protect and serve the people of California,' Brown said.