Read Peter Boyle's NYT Obituary here:
Peter Boyle was born on Oct. 18, 1935, in Northtown, Pa. After graduating from La Salle College, he became a member of the Christian Brothers order and entered a monastery as Brother Francis. He later recalled praying “so hard, I had calluses on my knees.” After three effortful years, he left the monastery — he later called it “an unnatural way to live” — and, after a brief period in the Navy that ended in a nervous breakdown, came to New York City to try the life of an actor.
There, he studied with Uta Hagen, worked at whatever jobs he could find, toured with a road company of Neil Simon’s “Odd Couple” and wound up in Chicago, where he joined the Second City troupe and immersed himself in improvisational theater. He was living in Chicago at the time of the Democratic National Convention in 1968 and never forgot the ensuing explosion of violence and the reek of tear gas in the streets. Early on, he described himself as a “conservative radical.”
I think it's also worth mentioning Boyle's film debut was in Sydney Lumet's adaptation of the Mary McCarthy novel The Group. Also he was in Taxi Driver, your favorite movie!