A second victim, an 18-year-old male from Toronto, remains in hospital in stable condition.
The stabbing happened just after 12:30 a.m. Sunday as the amusement park's late-night "Halloween Haunt" event was wrapping up and people were walking to their cars.
Police believe an altercation between two groups of people happened inside the park then continued in the parking lot after closing.
Multiple people were stabbed in both altercations, according to police.
Detectives would like to speak to anyone who was in the lot, near Jane Street and Springside Road in Vaughan, Ont., at the time. Contact the homicide unit at 1 (866) 876-5423 x 7865, or Crime Stoppers at 1 (800) 222-TIPS.