Quirinus Quirrell is a wizard who finds one of Tom Riddle's horcruxes around March 1991. Tom Riddle then takes possession of Quirrell's body and assumes his identity to become a teacher at Hogwarts.
In June 1992, in a graveyard a few miles from Hogwarts and Hogsmeade (canon), Voldemort left Quirrel's body. Relieved beyond comparison, Quirrel could only yell "Free!… Free!!!" before Voldemort ruthlessly killed him in the process of making a horcrux for Hermione Granger.