Complex sentence: Stettner started working with UNIX while at Bell Labs Murray Hill and later moved to DEC where he worked for Bill Munson and with Fred Canter and Jerry Brenner to start DEC's UNIX Engineering Group.
Split into simpler sentences: Stettner started working with UNIX while at Bell Labs Murray Hill. He later moved to DEC where he worked for Bill Munson and with Fred Canter and Jerry Brenner to start DEC's UNIX Engineering Group.