Deshawn Thomas stands over David Saldana in this screengrab taken from surveillance footage.
CNN  — 

A man has been charged with murder in connection with a killing in St. Louis Monday that a witness captured on video, which appears to show a man being shot at close range while sitting on a sidewalk downtown at about 10 a.m.

The St. Louis Circuit Attorney’s Office issued charges for first-degree murder and armed criminal action against Deshawn Thomas, 23, after, according to a St. Louis Metro Police Department probable cause statement, officers responded to a call of a shooting and found David Saldana dead on the sidewalk on N. Tucker Boulevard.

“Investigation revealed the incident was caught on surveillance, which depicts the Defendant following the Victim across the street, and first shooting him in the back,” the statement said. “As the Victim begged for his life, Defendant loaded his firearm and shot him in the head.”

Deshawn Thomas

In a news release, St. Louis Police said Saldana and Thomas got into a fight at a nearby gas station shortly before the shooting.

Police said Thomas was later taken into custody trying to enter a library and officers found a firearm and shell casing on him.

CNN has been unable to identify an attorney for Thomas, but according to the St. Louis Circuit Attorney’s Office, he has an initial court appearance scheduled for Wednesday in the 22nd Judicial Circuit Court.

A witness shared video purporting to be of the incident with local media and it made its way to social media.

The St. Louis Metro Police Department declined to confirm the video showed the shooting, but CNN was able to geolocate it to the approximate address reported by police.

The video shows a man laying on the sidewalk as another man walks away from him and then walks back toward him. After a short time, the man on the sidewalk sits up while the other man stands over him. Then, the other man appears to load a gun, point it at the man’s head and fire. The video does not include any audio of a conversation between the two men.