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NEWMAN, Stanislaus County — A manhunt for a suspect in the fatal shooting of a small-town police officer in Stanislaus County intensified Thursday — the same day officials announced that the suspect was in the country illegally, prompting President Trump to seize on the shooting in his fight over border security.

“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,” Trump wrote on Twitter, propelling the case into the national spotlight. “Time to get tough on Border Security. Build the Wall!”

The comment came as law enforcement in Newman said they know who the suspect is. But officials did not release the suspect’s name or country of origin. They did not explain how they determined he is in the country illegally, and they did not say whether he has a criminal record or was previously deported.

Members of the 13-officer force were overwhelmed by the slaying of their colleague, identified as Officer Ronil Singh, a 33-year-old husband and father who was shot at 1 a.m. Wednesday while conducting a DUI stop on a Christmas night shift.

“We will relentlessly continue to hunt our suspect down and bring him to justice,” Stanislaus County Sheriff Adam Christianson said at a news conference. “This has a very unique impact on a community that’s very small.”

Authorities released an alert to law enforcement around California describing the suspect as “heavyset” and wearing a silver necklace and a black sweatshirt with white patches on the shoulders.

Surveillance photos of the suspect show him prior to the shooting inside the Newman Food Store, where he purchased two 12-packs of beer before driving away in a gray Dodge Ram pickup truck with paper plates. Late Thursday, Stanislaus County sheriff’s officials released new photos of the suspect, saying they are circulating on social media. But they still were unable to release a name, they said.

Employees at the store recognized the man as someone who frequents the store, but owner Yoon Kim said she did not know his name.

Singh pulled the driver over a quarter mile away from the store near Merced Street and Eucalyptus Avenue, where the gunman opened fire. Singh was hit multiple times and called out “shots fired” over his police radio before paramedics arrived and rushed him to a hospital, where he was pronounced dead.

Authorities found the Dodge truck Wednesday afternoon near the Fisherman’s Bend mobile home park in town, where officers conducted a door-to-door search for the suspect as police helicopters circled overhead.

On Thursday, a tip prompted detectives to serve a search warrant on a property in El Nido in Merced County, but officials did not find the suspect.

The California Highway Patrol, sheriff’s offices and police departments around the state were joining the effort to track down the gunman.

“We have a lot of manpower out right now actively searching for our suspect,” said Sgt. Tom Letras, a Stanislaus County Sheriff’s Department spokesman.

Newman, home to 10,000 residents, is mostly known for growing almonds. Many of the town’s smaller dairy farms had to shut down in recent years because of the high cost of operations, Mayor Bob Martina said.

But the community is tight-knit and surrounded by green farmland. On Thursday a memorial of flowers, candles and balloons grew against the front doors at police headquarters. The marquee on the town’s movie theater read “Ronil Singh Forever Remembered.”

Some residents said they recognized the suspected shooter from a convenience store at the mobile home park on a rural road near the San Joaquin River.

“He would come in and buy beer,” said Kathy Sweetwater, who works at the store. “I wouldn’t see him buy anything else. He never said anything. He was always quiet.”

President Trump said the incident proved the need for a wall on the Mexico border. The contentious issue is central to the current government shutdown. But many residents in Newman rebuffed the president’s comment, choosing instead to focus on the tragedy facing their community.

“I don’t think it should be about the wall at all,” said Veronica Miller, 45, who works at a gas station in town. “I think that’s the whole Newman mentality: We all sort of stick together. Everybody in this town knows each other.”

The killing was the first line of duty death in the small Police Department’s history.

“He loved being a police officer,” Police Chief Randy Richardson said, tears at times streaming down his face as he spoke Thursday. “He loved being a husband. He loved being a father.

“My department is hurting. We’re struggling through this.”

Singh was a native of Fiji who studied criminal justice at Modesto Junior College and had achieved his dream of becoming a police officer. He lived in Modesto with his wife, Anamika, and their 5-month-old son.

On Thursday evening, dozens of his family and friends gathered at his home. A bouquet rested on a planter outside. Blue ribbons were tied to the trees in the neighborhood. A patrol car idled out front. A man in a pickup truck drove by and called out, “I just want to offer my condolences,” as more people filed into the home.

Singh joined the Newman Police Department in July 2011.His one purpose in coming to this country was to become a police officer, Richardson said, adding that Singh was one of his first hires and had dreams of one day leading the department.

He had recently tested to become a sergeant, and his latest role was that of a K9 officer. His canine partner, Sam, was in the car with him when he stopped the suspect.

Sam will be retired and stay with Singh’s wife and son, police said.

Henry Castaneda, 59, said he would often see the officer in his neighborhood checking on a parolee who lived next door to him. Singh would always knock on his door to say hello, and when driving by he’d honk his horn and wave.

“It’s a family here, everybody knows everybody,” Castaneda said, adding that his 7-year-old granddaughter and 5-year-old grandson went to the police station Wednesday night to light a candle in Singh’s honor. “This is personal.”

Newman is the kind of town where residents gathered two weeks ago for a parade and Christmas tree lighting involving the high school, junior high and several elementary schools.

The mayor remembered Singh’s enthusiasm the day he was sworn in as an officer.

“This was his life and this is what he wanted to be,” Martina said. “We were so proud to have him.”

The mayor recalled being attacked by a pit bull and Singh being the responding officer. He said he will never forget Singh’s help.

“He was so concerned,” Martina said. “He wanted to help in any way he could. You can tell when somebody cares and when they truly want to help you.”

The officer’s slaying is especially heartbreaking, Martina said, because Singh and his wife had a baby boy.

“He will never have the opportunity to see him walk or see him talk,” he said.

San Francisco Chronicle

staff writer Lauren Hernandez contributed to this report.

Sarah Ravani and Evan Sernoffsky are San Francisco Chronicle staff writers. Email: sravani@sfchronicle.com esernoffsky@sfchronicle.com Twitter: @SarRavani @EvanSernoffsky