WASHINGTON — President Trump pointed to a new reason Thursday to build his border wall — authorities said a gunman who killed a California police officer was in the US illegally.

“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.

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

Officer Ronil Singh was killed Wednesday during a traffic stop in Newman, a city of 11,000 about 70 miles east of San Jose.

Authorities said they believe they know the attacker’s identity but declined to release it.

But they also said he is not a legal US resident.

“This suspect … is in our country illegally. He doesn’t belong here. He is a criminal,” Stanislaus County Sheriff Adam Christianson told reporters.

A manhunt was underway for the attacker.

In his flurry of Thursday afternoon immigration-related tweets, Trump also dug up a 2011 Twitter note from former President Barack Obama. “I strongly believe that we should take on, once and for all, the issue of illegal immigration,” Obama wrote at the time. “I totally agree!” Trump chimed in.

Obama was set to sign a 2013 immigration deal that passed the Senate, applauding it for providing “the most aggressive border security plan in our history.” But Republicans killed it in the House.

Trump blamed the Democrats for obstructing his plans to boost border security – with his wall – announcing that “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,” Trump continued.

While the president was complaining about the alleged cop-killing illegal immigrant, the Senate was in the process of meeting and adjourning after just four minutes, ensuring the government shutdown would last several more days over funding for the border wall.

The Senate and House won’t come back into session until Monday, expected in both to be a short, pro forma session only. The Senate will then return Wednesday, the day before the new Congress, with a Democrat-led House, takes over.