Nucky's most famous line explains why Boardwalk Empire killed off Jimmy

Here's what really happened

The line is "You can't be half a gangster," and Jimmy Darmody says it to Nucky Thompson in the pilot. Winter has said the writers decided at the start of season 2 that Nucky's arc had to end with him pulling the trigger himself — on the man who gave him that advice. Jimmy dies in the finale, "To the Lost," which aired December 11, 2011.

Whose line it actually is

Worth clearing up, since the show's marketing blurred it: Nucky doesn't actually say it. Jimmy does, in the first episode, after Nucky warns him he could have him killed. Jimmy's answer is that Nucky won't, because he can't be half a gangster anymore. Nucky's reply is a flat acknowledgment that Jimmy now understands the arrangement.

Two seasons later, Nucky shoots him in the face in the rain at the Atlantic City war memorial.

Winter's reasoning

Speaking to Entertainment Weekly after the finale, Winter said he'd made the call at the very beginning of season 2, and that the logic of the season left no alternative — Jimmy had betrayed Nucky and tried to have him killed.

"Anything short of Nucky doing it himself wouldn't feel real," Winter told Entertainment Weekly in 2011.

He made a related point to TVGuide.com the following year: through 11 episodes of season 2, Nucky had never fired a shot himself. He was the man who told other people to do it. After the finale he was both.

But what about the Michael Pitt rumors?

The timing gave everyone plenty to work with. The sequence:

• October 2011 — Deadline reports that UTA dropped Pitt as a client, describing him as difficult on set and otherwise.
• December 11, 2011 — the finale airs. Jimmy dies. Fans flood Twitter.
• December 12, 2011 — Winter tells EW the backstage story is not true, calls Pitt a total professional, and says the decision predated everything by a year.
• Same week — Pitt tells EW he liked the storyline, and that he's always drawn to something shocking.
• June 2012 — Winter admits at a Hollywood Reporter roundtable that Pitt learned about the death by email, blaming bad cell service and Martin Scorsese's schedule.

Anonymous accounts of on-set friction have circulated for over a decade. None has been confirmed by anyone with a name.

For the record: Winter told Slate in 2012 that Nucky spends season 3 carrying the damage of having killed a man who functioned as a surrogate son — and that the character starts chasing distractions to avoid thinking about it.