Torture Horror About Teens in Warehouse

by Paul
(UK)

Trying to find this film I watched circa 2000 in which a psychopath tortures someone tied up and hanging in a warehouse. This is witnessed by teenagers who the killer goes after as well.

In one scene, a male victim is hiding on top of a small enclosure (an elevator?) as the killer searches for him. When the killer goes to leave, he instead pulls a sliding cage door shut, trapping them both in, then stabs him to death.

Any ideas?