An unknown man opened fire in an apartment on the city's Southwest Side, killing three people and seriously wounding two, AP  reported.

The incident occurred in Brighton Park neighborhood.

According to the police, two were killed on the spot and third others died in the hospital. An 18-year-old and a 19-year-old were fatally shot in the head.

Authorities say the circumstances surrounding the shooting were not immediately clear. Police say the victims were inside the apartment when an unknown male walked inside and began shooting.