A gunman who killed a California police officer during a traffic stop over possible drunken driving is in the United States illegally, authorities said Thursday, as a manhunt for the attacker stretched into a second day.

Stanislaus County Sheriff Adam Christianson said authorities identified but won’t yet name the man who killed Cpl. Ronil Singh of the small-town Newman Police Department. Authorities said they believe he’s still in the area some 100 miles (160 kilometers) southeast of San Francisco and is armed and dangerous.

“This suspect … is in our country illegally. He doesn’t belong here. He is a criminal,” Christianson, whose agency is leading the investigation, told reporters.

Newman Police Chief Randy Richardson fought back tears as he described Singh, a 33-year-old native of Fiji with a newborn son, as an “American patriot.”

“He came to America with one purpose, and that was to serve this country,” Richardson said.

Singh stopped the attacker Wednesday as part of a drunken driving investigation and fired back to try to defend himself, Christianson said.

Authorities are looking for a man seen in surveillance photos at a convenience store shortly before Singh was killed. Officials pleaded for help from the public and said they were following up on several leads.

“The sheriff’s office will spare no expense in hunting down this criminal,” Christianson said.

Singh was shot a few minutes after radioing that he was pulling over a gray pickup truck that had no license plate in Newman, a town of about 10,000 people. Singh died at a hospital.

A ground and air search began for the heavyset man pictured at the store with short, dark hair and wearing a silver chain, jeans, dark T-shirt and a dark jacket with white Ecko brand patches on the shoulders.

A truck believed to have been the one stopped by Singh was later found in a garage in a mobile home park about 4 miles (6 kilometers) from the shooting, where law enforcement officers were serving a search warrant, The Modesto Bee reported. Investigators were examining the vehicle, police said.

Singh joined the Newman police force in 2011. Richardson said that his department of 12 is grieving Singh, and other agencies are lending a hand.

“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.”

Ronil Singh was never in a bad mood and always had a smile on his face, Richardson said.

There is right now a full scale manhunt going on in California for an illegal immigrant accused of shooting and killing a police officer during a traffic stop. Time to get tough on Border Security. Build the Wall! — Donald J. Trump (@realDonaldTrump) December 27, 2018

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. His profile picture shows him smiling as he stands at a patrol car with his police dog — the same photograph of the officer released by the Sheriff’s Department.

Singh is survived by his wife, Anamika, and their 5-month-old son.

“Please help us find this coward,” Richardson said of Singh’s killer. “We need closure, his family needs closure.”

“Border Patrol Agents want the Wall.” Democrat’s say they don’t want the Wall (even though they know it is really needed), and they don’t want ICE. They don’t have much to campaign on, do they? An Open Southern Border and the large scale crime that comes with such stupidity! — Donald J. Trump (@realDonaldTrump) December 27, 2018

This isn’t about the Wall, everybody knows that a Wall will work perfectly (In Israel the Wall works 99.9%). This is only about the Dems not letting Donald Trump & the Republicans have a win. They may have the 10 Senate votes, but we have the issue, Border Security. 2020! — Donald J. Trump (@realDonaldTrump) December 27, 2018

The reason the DACA for Wall deal didn’t get done was that a ridiculous court decision from the 9th Circuit allowed DACA to remain, thereby setting up a Supreme Court case. After ruling, Dems dropped deal – and that’s where we are today, Democrat obstruction of the needed Wall. — Donald J. Trump (@realDonaldTrump) December 27, 2018

The Democrats OBSTRUCTION of the desperately needed Wall, where they almost all recently agreed it should be built, is exceeded only by their OBSTRUCTION of 350 great people wanting & expecting to come into Government after being delayed for more than two years, a U.S. record! — Donald J. Trump (@realDonaldTrump) December 27, 2018

Have the Democrats finally realized that we desperately need Border Security and a Wall on the Southern Border. Need to stop Drugs, Human Trafficking,Gang Members & Criminals from coming into our Country. Do the Dems realize that most of the people not getting paid are Democrats? — Donald J. Trump (@realDonaldTrump) December 27, 2018

(AP)