A 20-year-old man was fatally shot early Sunday in the Gage Park neighborhood on the Southwest Side, authorities said.

About midnight, Tontriche Weathersby Jr. was at a party in the 5800 block of South Maplewood Avenue when he got into an argument with a male who showed a handgun and then shot him in the chest, according to Chicago Police and the Cook County medical examiner’s office.

Weathersby, who lived in southwest suburban Evergreen Park, was taken to Holy Cross Hospital and pronounced dead at 12:20 a.m., authorities said.

Area Central detectives were conducting a homicide investigation.