Title: Nightmare Hall: The Night Walker
Author: Diane Hoh
Published: March 1994
When a mysterious night stalker begins roaming the campus and attacking people during the wee hours of the morning, all clues point to Quinn Hadley, a sleepwalker. (amazon.com)
That could be really good. A murdering sleepwalker? And all before the advent of Ambien! And people thought sleep-eating was bad.