LOS ANGELES (Reuters) - A suspect wanted in the shooting death of a California police officer was believed to be in the United States illegally, a county sheriff said on Thursday as President Donald Trump cited the manhunt in his push for a wall on the border with Mexico.

Trump tweeted about the shooting on the sixth day of a shutdown of the federal government, which was triggered by his $5 billion demand, largely opposed by Democrats and some lawmakers in Trump’s own Republican party, for the wall he wants to build.

A police officer for the city of Newman, a small Northern California town, was shot and killed there on Wednesday, after pulling over a suspect on suspicion of driving under the influence, authorities said.

The suspect, whose name has not been released, exchanged gunfire with the officer before fleeing, Stanislaus County Sheriff Adam Christianson told reporters. The officer, identified as 33-year-old Ronil Singh, was struck by gunfire and taken to a hospital where he was pronounced dead.

“This suspect is in our country illegally,” Christianson said at a news conference. “He doesn’t belong here, he’s a criminal. We will find him we will arrest him and we will bring him to justice.”

Trump, during his campaign for president and in the White House, has often highlighted crimes by people who came to the United States without authorization as he has pushed for tougher enforcement of immigration laws.

“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 tweeted on Thursday. “Time to get tough on Border Security. Build the Wall!”

Christianson did not give the nationality of the suspect or say how long he was believed to have been in the United States without authorization.

A Stanislaus County Sheriff’s Office spokesman could not be reached for further comment.

The suspect is believed to still be in Stanislaus County, a largely agricultural area less than 50 miles (80 km) east of San Jose, Christianson said.

Singh was a native of Fiji who immigrated to the United States to become a police officer, Newman Police Chief Randy Richardson told reporters.

“He was never in a bad mood, it was unreal, he loved what he did,” Richardson said at the news conference, breaking down in tears at times.

During the traffic stop, Singh told emergency dispatchers shots had been fired, authorities said, but the suspect fled in a Dodge Ram pickup truck before other officers could arrive.

(This story has been refiled to remove erroneous character in lead paragraph)