The shocking footage shows the assailant running up to the victim from behind Sunday evening and then striking him in the head with the brick, sending him headfirst to the pavement.
The assault happened after a “loud argument” between two men, according to a statement from an unnamed witness included in a police incident report.
WARNING: VIDEO MAY BE DISTURBING
The witness told investigators that as one of the men walked away, the other grabbed a couple of bricks and struck him with one.
Police responded at 6:40 p.m. to Hamburg Street in the Sharp-Leadenhall neighborhood, the Baltimore Sun reported.
An officer found a “pool of blood” on the sidewalk but did not locate the victim. The witness told police the attacker fled from the scene.
“It happened so fast,” one witness, who did not want to be named, told local CBS affiliate WJZ. “When I saw him running I thought he was running to talk to the guy.”
City Councilman Eric Costello, who represents the area, condemned the assault and asked people with information to come forward.
“It should go without saying that the complete depravity to human life illustrated in this video is absolutely disgusting and should be investigated and prosecuted to the full extent of the law,” Costello wrote on Facebook.