A 19-year-old man was fatally shot at 6 p.m. Thursday in the 4700 block of West Belmont in the Portage Park neighborhood on the Northwest Side, Chicago Police said.

The man was standing on the sidewalk when a gunman approached and shot him once in the back, police said. He was pronounced dead at Advocate Illinois Masonic Medical Center, authorities said.

Area North detectives were investigating.