The shooting occurred at about 12:05 a.m. in the 1300-block of West Estate Lane East.
The victim was identified as Shaft Wilson Jr., according to his father.
The victim and the shooter, who knew each other, were arguing outside the house when the incident occurred, said Christopher Covelli, spokesman for the Lake County Major Crimes Task Force. The shooter was not in custody Sunday night.
A 20-year-old female was also injured when she was trampled when partygoers were leaving the party. More than 100 people were at the party, Covelli said. The homeowners were not present, but the party was hosted by someone who lives at the house, Covelli said.
Police said that the shooting was not random and there is no danger to the community.
The victim's father went to the police station looking for answers.
"I just want to know what happened. How did he die, why did he die?" said Shaft Wilson, Sr.
Police were still at the house Sunday night and did not say whether they have a person of interest.
Anyone with information on the shooting is asked to call Lake Forest Police at 847-810-3818 or Lake County CrimeStoppers at 847-662-2222.