A St. Louis man was arrested Tuesday after video appeared to catch him nonchalantly shooting a homeless man execution-style in broad daylight.

Deshawn Thomas, 23, was arrested in connection with the Monday murder but has yet to the charged, police said.

Thomas can be seen struggling to load his gun as he stands right behind the homeless man, who is sitting on the curb just a few feet away, bystander video posted online shows.

He then appeared to fire on the yet-to-be-identified victim, who raised his arms at one point, but made no attempt to run away and seemed almost resigned to his fate, the video showed.

“Oh my god. He just f–king killed him,” the witness can be heard saying.

Deshawn Thomas, 23, can be seen on video struggling to load his gun as he stands near the victim in downtown St. Louis.

Police said the two men had a run-in at a nearby gas station minutes before the execution-style shooting.

The shooting happened in the heart of downtown St. Louis Monday at around 10 a.m., police said.

“Any homicide is unnerving,” Maj. Ryan Cousins told the St. Louis Dispatch at the scene, “but for this one to happen here, at this time, very much so.”

The victim, whose name has not been released, had fended off Thomas at a Shell gas station just minutes before. Thomas then chased him across the street before allegedly shooting him, police said.

.”Thomas was taken into custody by police at a local library after fleeing the scene.

Before the video of the Monday murder surfaced, Gardner was already under fire after a driver facing felony charges for robbery — who had violated his bail conditions multiple times — hit a teenager earlier this month, causing her to lose her legs.

Missouri Republicans have called for the state to handle the prosecution of violent crimes instead of Gardner, and filed court documents recently in an attempt to fire her.