The party took place on the evening of Friday, April 11. According to Durham Regional Police, some 200 to 300 people attended the event on Reytan Boulevard.
Police say that a group of youths targeted a 16-year-old, who was chased, beaten and stabbed.
The assailants fled the scene in a car. But the vehicle then came back and the victim was deliberately struck, police say.
The victim suffered serious, but non-life threatening injuries and ended up being treated in a trauma centre in Toronto.
Police believe the incident was likely recorded on cellphones. Investigators want to hear from anyone who attended the party or witnessed the attack.
Anyone with information is asked to contact investigators at 1-888-579-1520, ext. 2529.
Information can also be passed on anonymously via Crime Stoppers at 1-800-222-8477.Suggest a correction