The Justice Department has issued an arrest warrant for the Mexican immigrant acquitted Thursday in the 2015 killing of Kate Steinle in San Francisco, a case that has reignited a rallying cry for stricter immigration reform and a crackdown on so-called “sanctuary cities.”

An official confirmed to The Washington Post that the Justice Department is considering federal charges against  Jose Ines Garcia Zarate, who has remained in law enforcement custody. Officials said Garcia Zarate  — a 45-year-old Mexican national who had entered the United States illegally six times — will be deported. They noted that his existing federal detainer order requires that he be transferred to the custody of the U.S. Marshals Service and transported to Texas.

After six days of deliberations, a jury on Thursday convicted Garcia Zarate for unlawful possession of a firearm, which carries a sentence of up to three years. He was found not guilty of murder, as well of the lesser charges of involuntary manslaughter and assault with a deadly weapon.

“How you could come to that conclusion is a mockery of justice. I don’t know how else to put it,” said California State Senator Jeff Stone. “It should be a wake-up call to every American that our judicial system in certain parts of the country, such as here in San Francisco, are way off the charts to the left and have to be fixed.”

President Trump, who invoked Steinle repeatedly on the campaign trail as an example of the danger posed by illegal immigration, fired off a string of tweets Thursday night and early Friday morning, calling the verdict “disgraceful,” and warning that “The Schumer/Pelosi Democrats are so weak on Crime that they will pay a big price in the 2018 and 2020 Elections.”

Conservative pundits and media outlets erupted in outrage over the verdict Thursday night., run by former White House adviser Stephen K. Bannon, published at least eight related headlines on its homepage overnight, leading with “FIVE-TIMES-DEPORTED ILLEGAL ALIEN FOUND **NOT GUILTY**IN MURDER OF KATE STEINLE.”

San Francisco, where Steinle was killed, is considered a “sanctuary city,” in that local law enforcement authorities have declined to participate in immigration enforcement, which they say is the responsibility of the U.S. Immigration and Customs Enforcement (ICE).

Garcia Zarate had been released from jail, where he had been held on a marijuana charge, 2-1/2 months before the killing. Local officials had not notified ICE, which was seeking to deport him, and ICE had not presented the warrant needed to hold Garcia Zarate longer.

ICE Deputy Director Tom Homan blamed the city of San Francisco for Steinle’s death.

“San Francisco’s policy of refusing to honor ICE detainers is a blatant threat to public safety and undermines the rule of law. This tragedy could have been prevented if San Francisco had simply turned the alien over to ICE, as we requested, instead of releasing him back onto the streets,” Homan said in a statement Thursday.

The office of San Francisco Mayor Edwin M. Lee (D) released a statement Friday saying, “San Francisco is and will always be a Sanctuary City.”

Jim Steinle, Kate Steinle’s father, who was with her when she was shot, said he was “saddened and shocked” by the verdict.

“There’s no other way you can coin it. Justice was rendered, but it was not served,” he told the San Francisco Chronicle in an interview.

But he said the verdict marked an end to a painful period in the family’s lives.

“We just want to get this over with and move on with our lives, and think about Kate on our terms. Nothing’s been on our terms. It’s been on everyone else’s terms,” he told the newspaper.

Trump and other Republicans have used Steinle’s name over the past two years to justify Trump’s proposed border wall and his attempt to block federal assistance to sanctuary cities. They have also championed a piece of legislation dubbed Kate’s Law, that would enhance penalties for convicted and deported criminals who reenter the United States illegally. The bill passed the House in 2016, but stalled in the Senate, and has shown no sign of reviving.

“The death of Kate Steinle was a heartbreaking and preventable tragedy.  She died in her father’s arms at the hand of someone who violated our nation’s laws and who never should have been in our country,” Sen. Chuck Grassley (R-Iowa), the chairman of the Senate Judiciaries Committee and a co-sponsor of the Senate version of Kate’s Law, said in a statement Friday.

“The sad reality is that had local authorities cooperated with federal law enforcement, this could have been avoided. We must honor Kate’s legacy by taking steps to ensure that this does not happen again,” Grassley said. “The United States Senate should immediately pass Kate’s Law to improve community safety and prevent future tragedies.”

Immigration advocates argue that Steinle’s ostensibly accidental killing has been exploited to push forward sweeping new immigration policies, and unfairly vilify millions of undocumented immigrants.

“One unfortunate scenario shouldn’t be used to cast dispersions against every immigrant in this country and that’s what we see happening,” said Jennie Pasquarella, the director of immigrants’ rights and a senior staff attorney at the American Civil Liberties Union in southern California.

Kate Steinle, 32, was shot in the back on July 1, 2015, as she and her father strolled along Pier 14 in San Francisco. Steinle, who worked in sales for the medical device company Medtronic, had recently moved in with her boyfriend in San Francisco, according to the San Jose Mercury News.

As she walked with her arm around father, who lives in the Bay Area community of Pleasanton, they heard a gunshot, Jim Steinle would later testify before the Senate Judiciary Committee. The next thing he knew she had fallen to the ground.

“Help me, Dad,” were her last words, as she looked up at her father, he later said. The bullet hit Kate Steinle in the back and pierced her aorta.

She died two hours later at San Francisco General Hospital.

The fatal bullet came from a .40 caliber Sig Sauer P239 semiautomatic pistol that had been stolen from the car of a ranger with the Bureau of Land Management.

Garcia Zarate, who was homeless after being released from jail weeks earlier, had been wandering around the pier. The manner and intent with which Garcia Zarate obtained the gun and fired it were fiercely debated in court.

At the month-long trial prosecutors said Garcia Zarate arrived at the pier with the gun and deliberately fired it toward Steinle, according to the Chronicle.

Prosecutors showed video of Garcia Zarate’s police interrogation, in which he gave varying stories about whether he was actually present on Pier 14 that night. He said that he shot the gun at “seals” but also that it went off accidentally when he stepped on it, ABC 7 reported.

Garcia Zarate’s signed confession from that police interrogation was admitted into evidence at the trial. But defense lawyers questioned its validity, arguing that police had lied to Garcia Zarate, telling him they had recovered the weapon and found a DNA match that implicated him, which had not happened at the time.

They said Garcia Zarate found the gun wrapped in a cloth on the pier and that it discharged accidentally as he held it, with the bullet ricocheting off the concrete before striking Steinle.

He hurled it into San Francisco Bay, not to hide his crime, as prosecutors contended, but because he was scared by the noise of the weapon.

During deliberations, according to the Chronicle, jurors asked if they could test the trigger of the pistol, presumably to see if it could fire accidentally. The judge denied the request.

Garcia Zarate’s time in court ended up being one of the most politicized criminal trials in years, with the court handing out spots in the courtroom by lottery, and the judge instructing jurors to ignore the swirling politics around the case.

In releasing Garcia Zarate, who had a history of nonviolent crimes, the sheriff at the time said he was following San Francisco’s sanctuary policy, which limited the cooperation of local law enforcement with immigration authorities.

The sheriff, Ross Mirkarimi, was later defeated in a bid for reelection, in part because of the case, according to the Chronicle.

Steven Camarota, the director of research at the Center for Immigration Studies, an organization that advocates for strict limitations on both legal and illegal immigration, said the verdict could have an impact on the ongoing Congressional battle to resolve the status of the nearly 700,000 people who were granted temporary protection from deportation under the Deferred Action for Childhood Arrivals (DACA) program started by President Obama.

Those who want to crack down on immigration want to see stricter provisions put into place before any DACA-recipients are allowed a path to renewed or permanent legal status.

“The idea is that if you give legal status to illegal immigrants you’re going to encourage more illegal immigrants in the future,” Camarota said.

Jim Steinle has filed a wrongful-death suit against the city and county of San Francisco and the U.S. government. But the family has objected to the way Kate’s death has become a political football.

Kate Steinle’s brother, Brad, has criticized Trump for “sensationalizing” Kate’s death to advance his immigration proposals, particularly his plan to build a wall along the U.S.-Mexico border.

“Donald Trump talks about Kate Steinle like he knows her,” Brad Steinle said in a CNN interview in 2015.  He added, “I’ve never heard a word from him. I don’t want to be affiliated with someone who doesn’t have the common courtesy to reach out and ask about Kate, and our political views and what we want.”

The bill, named after a woman who was killed by an illegal immigrant, seeks to toughen punishments on people who reenter the U.S. illegally. (Claritza Jimenez/The Washington Post)

Abigail Hauslohner in Washington and Alissa Greenberg in Berkeley, Calif. contributed to this report.