The suspected gunman sought in the killing of a California police officer is an immigrant living in the country illegally, and the police chief of the small department called the slain officer "an American patriot."

Newman Police Cpl. Ronil Singh, 33, was shot and killed after pulling over a vehicle in a driving under the influence investigation minutes before 1 a.m. Wednesday. Moments later, he called out "shots fired" over his police radio, the sheriff's department said in a statement. The officer returned fire in what was described as a gunfight, the sheriff said.

"I do not want to be here today. I would give anything not to," Newman Police Chief Randy Richardson said Thursday at a news conference, where he spoke emotionally about Singh, who immigrated to the U.S. from Fiji and was a husband and the father of a 5-month-old son.

A suspect police are searching for in connection to the fatal shooting of an officer during a traffic stop in Northern California. Stanislaus County Sheriff's Department / via AP

"I did not know Christmas morning, at 4 o'clock in the morning when I said goodbye to him and sent him off to his family that it would be the last time that I saw him," Richardson said.

The manhunt for the gunman continued Thursday.

Authorities said the pickup truck believed to have been driven by the suspect was recovered Wednesday just outside Newman, a city of about 10,000 people some 80 miles southeast of San Francisco.

NBC affiliate KCRA reported that the truck was found in a garage at a mobile home park around 4 1/2 miles from the location of the traffic stop.

Stanislaus County Sheriff Adam Christianson said they have identified the suspect, who was living in the U.S. illegally, but authorities have not released his name.

"We have multiple teams out following up every lead, and we will relentlessly continue to hunt our suspect down and bring him to justice," said Christianson, whose department is leading the investigation.

"This suspect — unlike Ron, who immigrated to this county lawfully and legally to pursue his lifelong career of public safety, public service and being a police officer — this suspect is in our country illegally," the sheriff said. "He doesn't belong here. He's a criminal."

Christianson said the Newman Police Department, which Richardson described as "a department of 12," had never before suffered a line of duty death.

Singh and the suspect were engaged in "a gunfight" when he was killed, Christianson said.

"Cpl. Singh absolutely tried to defend himself and stop this credible threat," he said.

The suspect is considered armed and dangerous, Christianson said. Police have no evidence to suggest the suspect was wounded in the exchange of gunfire, the sheriff said.

"We will find him, we will arrest him, and we will bring him to justice," Christianson said.

Singh joined the Newman Police Department in 2011. Earlier in his career, he was a reserve deputy with the Merced County Sheriff’s Office and is remembered fondly, the agency said in a statement.

Richardson said "he wanted to serve this country" and remembered Singh as "an American patriot," and that he loved being an officer, husband and father and enjoyed hunting, fishing, spear-fishing and riding Jet Skis.

"He will never see his son walk. He doesn't get to hold that little boy, hug his wife, say goodnight anymore — because a coward took his life,” Richardson said. He encouraged anyone with information to call police and the suspect to turn himself in.

President Donald Trump on Thursday tweeted about the killing: “Time to get tough on Border Security. Build the Wall!”

Trump in the past has highlighted crimes committed by those in the U.S. illegally and made border security and immigration a key part of his campaign.

Singh's police dog, Sam, was not injured in the shooting. The dog is with the Singh family and will be retired, Richardson said.

"She probably does have more time that she could work the streets, but I will not take another member of that family from them," he said. "That was a member of their family."