Two men, ages 41 and 30, died from their injuries, and two men, ages 37 and 38, are in critical condition.
Detectives learned a group of gang members were at the nightclub and were initially refusing to leave at closing time.
Officials say the investigation is active and that investigators are still working to identify the shooter.
The justice department confirmed its ongoing investigation but did not furnish further details.
The nature of the relationship between the suspect and the victim remains unclear at this time, according to authorities.
After the shooting, the shooter fled the area.
One of the wounded individuals has been discharged from the hospital.
Police ask public to please stay out of the area.
Authorities are also investigating whether two drivers may have been street racing at the time of the collision.
Residents should avoid 1100 block of Fargo Avenue, police say.