HOLLYWOOD — As far as deaths on “24” go, the one last week was fairly quick and painless.

At least it was for actor James Morrison, who played Jack Bauer’s coolheaded boss Bill Buchanan for the past four years. But longtime fans of the Fox action drama, starring Kiefer Sutherland, still might have been a little shellshocked.

Buchanan goes out on his own terms — he blows himself up alongside a group of terrorists who have overtaken the White House. The character’s death ends an unexpected run for the actor, who was supposed to be a one-appearance guest star who soon became the ongoing source of pushback for Jack.

“The moment you step aboard ‘24’ you’re taught to expect that you’re going to bite it,” Morrison, 54, said in an interview. “In this solar system you have one sun. The rest of us are just planets that are invited to orbit, and sometimes we’re just yanked out of the sky.”

There have been plenty worse ways for good guys on the show to die: Lynn McGill died foaming at the mouth after inhaling nerve gas — ditto for agent Edgar Stiles. Meanwhile, Michelle Dessler was rubbed out by a car bomb, Counter Terrorist Unit director Ryan Chappelle was unceremoniously executed by Jack himself, and President David Palmer was assassinated.

This season, “24” has spent much time confronting its own controversial theme: Jack’s use of torture to extract information from terrorists. The season launched with CTU disbanded and Jack standing trial for his illegal methods. Buchanan had gone underground — sporting the 5 o’clock shadow and dramatic all-black get-up to prove it — working with computer whiz Chloe (Mary Lynn Rajskub) to suss out a mole in the FBI.

In one episode, Buchanan clashed with Bauer over torturing a compromised government official. Buchanan refused to do it.

“It was nice that Bill [Buchanan] didn’t have to become someone else,” said Morrison, a certified yoga instructor. “It was more in character to have him say, ambiguously as he did, ‘I can’t do that. Not only am I not trained to do that, but I can’t do that. That’s not me.’ ”

For his final goodbye, cast and crew gathered with cake on the White House set.

“I spent a moment with them basking in their appreciation of what I felt like was sort of a family member leaving the fold,” Morrison said. “It was the most familial set I’d been on.”

Since he’s been assured Bill’s staying dead (onetime dead agent Tony Almeida was resurrected this season), Morrison plans to record some of his own music — “blues, folk stuff,” he says — and finish work on “Showing Up,” a documentary he’s producing with his wife, Riad Galayini, about the audition process for actors.

He’ll also appear in the final two episodes of ABC’s “Private Practice.” “I can only reveal that I play someone who comes in to shake things up at the clinic,” he said.

“It was so great to do something where there’s no angst,” he added. “Where you’re just having a conversation with somebody and the safety of the world is not at stake.”