Armed men showed up at the party, which was attended by more than 100 people.
The incident occurred in the American city of Philadelphia on the night of July 21.
Pennsylvania State Police are investigating a high-profile shooting at a party attended by up to 150 people.
NBC News reports that three people were killed and seven others were injured.
The party took place on the night from Saturday to Sunday. At about two o'clock in the morning local time, several armed men arrived.
Police believe the main target was a 33-year-old man who was shot at close range and died at the scene.
The exact number of shooters is not known. The police are looking for suspects. After committing the crime, they disappeared in an unknown direction.
At the scene of the incident, law enforcement officers found about 30 shell casings from one abandoned firearm.
