The shooting, captured on a South Side gas station's surveillance camera, shows four men inside the vestibule of a GoLo gas station around 2am on March 10, 2017.

As two of the men talk, the gas station's bulletproof door opens and a gunman fires more than a dozen shots inside.

The four men are trapped inside the vestibule because the main door to the gas station is locked at night.

With nowhere to go, they drop to ground, clinging to each other.

Police said two of the men were shot multiple times and died. They were identified as J. C. and L. C., both 24.

The other two suffered non-life-threatening injuries and survived the attack.

One of them was a 25-year-old man who was not named, and the other was a 64-year-old man known in the city as Old Man Bill.

Residents said Bill, whose real name is David Scott, did odd jobs at the gas station.

Authorities said the gunman jumped out of a car outside the gas station, opened the door and started shooting. It's not clear what led to the attack or if the shooter was ever arrested.

The graphic video surfaced online this week following a deadly weekend in Chicago which saw 75 people shot, a dozen of them fatally.

According to reports, the shootings happened during the first weekend of August, making it the deadliest weekend of the year in the city.

So far, police have charged only one man - and are asking for the public's help in order to make more arrests.