BlakeDavidTaylor/iStockBy ALEXANDER MALLIN, ABC News

(KANSAS CITY, Mo.) — The Kansas City, Missouri, Police Department announced on Thursday the arrest of a suspect in the murder case of 4-year-old LeGend Taliferro, whose tragic killing in late June inspired the namesake for the Justice Department’s “Operation Legend” law enforcement initiative.

Police charged 22-year-old Ryson Ellis with second-degree murder, unlawful use of a weapon and two counts of armed criminal action, saying in a press release that Ellis fired shots into the apartment where Taliferro was sleeping on the night of June 29.

The KCPD said that Ellis sent threatening social media messages to a witness after the shooting, which led to Taliferro’s family members confronting him about the shooting, including Taliferro’s father.

Both Attorney General William Barr and President Donald Trump applauded the news of Ellis’ arrest, with Trump holding up a picture of Taliferro at a news conference at the White House.

“We named ‘Operation LeGend’ after LeGend Taliferro, where we are going to be helping out and are in the process of helping out cities throughout our country that have difficulty with crime,” Trump said. “So that’s really good news, they caught the killer of LeGend.”

In a separate statement, Barr said the arrest came as a result of coordination between Kansas City police, the FBI and agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives.

“Today’s arrest of LeGend Taliferro’s suspected murderer marks a significant step forward in his case and illustrates the potential of Operation Legend more broadly,” Barr said. “This development is a model for joint efforts to solve crimes and reduce violence in other cities. I thank the state and local law enforcement officers who helped make possible this important step in bringing justice to LeGend, to his family, and to his community.”

Barr first announced the creation of “Operation LeGend” in an exclusive interview with ABC News last month, when he told Chief Justice Correspondent Pierre Thomas that he decided to name the initiative after LeGend after hearing he had survived open heart surgery, only to be killed in his sleep.

“My daughter had open-heart surgery at a comparable age and I remember how stressful it was for our family,” Barr said at the time. “And the idea of your child surviving that and, you know, the– the joy you would feel to see your kid pull through something like that and then have them shot in the face, it — it affected me a lot.”

Since its launch in Kansas City, the DOJ has expanded Operation LeGend to multiple other cities, including St. Louis, Cleveland, Detroit, Milwaukee and Memphis, Tennessee.

The effort involves the deployment of agents from the FBI, ATF, Drug Enforcement Administration and U.S. Marshals to assist in investigating violent crimes in cities that have experienced recent surges. But it has been met with considerable skepticism, at least initially, from local leaders who believe Trump and Barr are working to target cities led primarily by Democrats with aggressive and visible federal responses like have been seen in Seattle and Portland.

Barr has repeatedly sought to separate “Operation LeGend” from the violent clashes in Seattle and Portland between protesters and federal agents primarily from the Department of Homeland Security.

“Although LeGend’s suspected murderer has been arrested, Operation Legend will go on,” Barr said Thursday. “Inspired by this success, federal law enforcement will continue working tirelessly to support state and local partners in our shared mission to keep the American people safe and enforce the rule of law.”

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