A school staff member discovered the body on the campus at 400 Lomond St. in Boulder Creek at about 7 a.m., Haff said.
It was on a balcony inside the school building.
Haff said she doesn't know the man's identity but that he is not a staff member.
A truck found near the school is thought to have belonged to the victim, authorities said.
The man's identity is known, but was not released by police as of 12 p.m. Authorities did confirm he was from out of the area.
Classes were canceled at the school for the day. Students at the school were set to return to school for the first time Monday after a week off for spring break.Counselors will be at the school on Tuesday when students return.