Timothy was born in in Honolulu, Hawaii, but moved to Modesto, a small agricultural town in Northern California at the age of two. He grauduated from Fred C. Beyer High School in Modesto in 1986 and then migrated south to Los Angeles to attend the University of Southern California, where he swam competitively.
He first came to audience's attention in "Scream," then followed that with memorable performances in "Go" and "Dreamcatcher." He gained cult fame after playing a gay softball player in "The Broken Heart Club."
His big break came when he was cast as the nominal hero, Seth Bullock, in the HBO drama "Deadwood."
He is married to Alexis Knief, with whom he has three children.