Alex O'Loughlin, Mark Dacascos Alex O'Loughlin, Mark Dacascos

Hawaii Five-0's 100th episode was a turning point for the show in more ways than one. In addition to hitting the milestone, the hour ended with the shocking death of Wo Fat (Mark Dacascos), the character who's been the nemesis of Steve McGarrett (Alex O'Loughlin) dating back to the original series.

And make no mistake — Wo Fat is definitely, definitely dead, assures executive producerPeter Lenkov. "It's not one of those, I was wearing a Kevlar vest, or you didn't see me after the camera left. I got up. I'm still breathing," Lenkov tells TVGuide.com. "He's dead. He's got a bullet in his head and there's no coming back from that."

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Before getting shot by McGarrett, Wo Fat finally spilled the beans about his true connection to McGarrett's mother. Turns out Doris felt so guilty over the death of Wo Fat's mother that she took him in as a baby and raised him for several years — until her superiors got wind of what she was doing and made her abandon him as a child.

TVGuide.com chatted with Lenkov about the decision to kill off Wo Fat, as well as where McGarrett will go from here. Check out our exclusive interview:

TVGuide.com: How and when did you decide that Wo Fat had to die?
Lenkov: 
It's funny. When I wrote the outline [for the episode], he wasn't dead in the outline. And when I started writing the script, it really felt like a natural end to the episode. I had always envisioned following the pattern of the original show, with the last show that we ever do being the capture of Wo Fat. But I felt, when I was writing it, that that felt a little predictable for people who watch the show and know the original one. They're going to be expecting that. And I felt like if I was going to surprise the audience at any point, this would be it. When I started writing it, at the end it just felt like such closure to the story. I think the audience responded the way I was hoping they would, which was [being] surprised. Obviously they'll miss Mark and Wo Fat, but that's a tribute to Mark's great acting. And we go on from here.

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How did you break the news to Mark Dacascos, and what was his reaction?
Lenkov: 
The hardest thing that I've had to do on the show was tell him his character was coming to an end.  ... I worked with him on The Crow years ago, so I've known him for a long time. And he's always been such a gracious, great guy. Every time you do work, you want to work with guys like that. And I think he understood. We had the conversation, and there was never a moment where he hesitated and said he didn't understand the choice. I think he got it and thought it was a good script, and he thought it was a great way to end his character.

Is there a chance he'll appear in flashbacks in future episodes?
Lenkov: 
Personally, I'd love to figure a way to do that because he was so good and I think it would be a nice way to keep him in the family. ... I'll work with him again in a second. Who knows? Maybe there's a flashback episode somewhere down the road that he comes back in. but unfortunately, his days as a nemesis in our world are over.

What was Alex O'Loughlin's reaction?
Lenkov: 
To be honest, I don't even think Al and I actually talked about it post-reading the script. Other than just him liking the script, I don't think there was an opinion either way about the choice. ... Everybody was surprised. I did hear from everybody saying, 'Wow.' Especially the description of his death, where I was very clear to the reader that he is not coming back.

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Obviously with Wo Fat dead, a burden has been lifted off of McGarrett. But he also has this new information to grapple with, about his mother and her connection to Wo Fat. How will this affect McGarrett going forward?
Lenkov: 
Now that he has this new information, I think there'll probably be at some point an episode where he's going to end up meeting Wo Fat's father. I think that's destined to happen. But I think for him it's really about finally locating his mother and getting some kind of closure to this whole thing. And I think once that's done, he can maybe sleep a little more peacefully.

Do you see that happening later this season, or further down the road?
Lenkov: 
(Laughs) Who knows? I'd love it to happen sooner than later.

Now that we're a few days out, do you think you made the right call in killing off Wo Fat?
Lenkov: If you think about the story, it really does make sense that it ended that way, and especially at the 100th episode. ... If he had gotten away at the end, I think it may have seemed ridiculous.

Will you miss Wo Fat?

Hawaii Five-0 airs Fridays at 9/8c on CBS.

(Full disclosure: TVGuide.com is owned by CBS.)