Complex sentence: Dorothy Podber (1932--2008) was an American was a performance artist best known for turning up at Andy Warhol's studio and putting a bullet through a stack of his silk-screen paintings of Marilyn Monroe.
Split into simpler sentences: Dorothy Podber (1932--2008) was an American performance artist. On one occasion, this led to an incident in which she turned up at Andy Warhol's studio and putting a bullet through a stack of his silk-screen paintings of Marilyn Monroe.