A 20-year-old man was shot in the head in South Philadelphia's Point Breeze neighborhood on Monday night, police said. 

The shooting happened at 19th and Ellsworth streets just after 9:30 p.m., according to police.

Police said on Tuesday that officers were flagged down by a person near the intersection of 18th and Fitzwater streets for a possible shooting and found the 20-year-old man lying on the sidewalk with a gunshot wound to his head. He was unresponsive and taken to Jefferson Hospital in critical condition, police said. 

Philadelphia Police Department Chief Inspector Scott Small said officers found one spent shell casing from a semiautomatic weapon at the scene right next to the male, which means he was likely shot at close range. 

Small said police also found a cellphone, mask and car keys, but it's unclear who they belong to.

Police are hoping to use private surveillance footage from the intersection of 19th and Ellsworth streets to help with the investigation. 

So far, no arrests have been made. 

A motive for the shooting isn't clear at this time, Small said.