Nat Geo's "Killing Kennedy" broke records for the network, drawing in the most total viewers (3.4 million) of any program in the network's history. If you haven't seen it, you can catch the encore this Fri. Nov. 15 at 8:00 p.m. and 10:00 p.m. (and watch a deleted clip from the film). But if you have seen it, you probably have a question -- who was that guy who played Lee Harvey Oswald, anyway? In a movie full of name brands (Rob Lowe, Ginnifer Goodwin, Michelle Trachtenberg) he was the unknown quantity, which seemed fitting for the person playing an assassin we think we know but probably don't.  

Will Rothhaar isn't a household name yet, but his searing portrayal of the man who fired that fatal shot from the book depository in Dallas might take him halfway there. I had a chance to hang out with Rothhaar during a visit to Dallas and found that, whatever the buzz might be, he's just a devoted actor who dug in deep.

It could easily be argued that he was meant to play this role -- he jokingly describes his parents, actors Michael Rothhaar and Nancy Linehan Charles, as Kennedy "freaks." As a kid, he listened obsessively to the album for the musical "Assassins" (something he dragged out again as bedtime music during filming). He told me that finding the way into Oswald wasn't about unraveling a monster, but realizing the killer was once a little kid who had a hard, hard life (one we don't see onscreen, but we get a glimpse of in the deleted scene). When Rothhaar says he wished he could have played baseball with that young version of Oswald, it's seems like a sincere sentiment, not cheesy actor spin. 

While I talked to Rothhaar many times during my trip (and watched the surreal moment when he visited Oswald's grave), I eventually pulled him aside for an interview almost as an afterthought. He'd been such a steady, low-key presence on the trip, it was easy to forget that in many ways he is the star of the show -- that is, until we watched the movie. Then, there was no denying it. I asked Rothhaar what's next, what it's like to play a famous villain, and how he will feel about awards buzz. It's way too early to ponder, sure, but if you've seen "Killing Kennedy," you'll get it.

In bringing Oswald to life, was everything on the page, or was there an element of you working with [director] Nelson McCormick and [screenwriter] Kelly Masterson?

All three of us collaborated on a whole lot of stuff. We got into the habit of doing this; I would walk onto the set to shoot a scene, and Nelson would say, "Come here. Where did you just come from?" And I would say something like, "Before this I must have just flown in to Houston, which means I took the bus to Dallas, which means I just got into the Greyhound station and I'm sure it was a long bus ride. I'm tired, sweaty, whatever." It was little things like that. It was just finding the moments to figure out where I came from. We would even start scenes with stuff that wasn't on the page and just roll into it, and he'd roll the camera and we would just go. Not that he used any of it, but it helped to get us into the here and now. 

Given that Rob Lowe and Ginnifer Goodwin are given pretty meticulous makeovers to become the Kennedys, why wasn't your hair darkened like Oswald's? 

They actually darkened my hair a little bit. They blew in black powder stuff. When I booked this, I had literally just walked out of the barber shop and had gotten a bald fade, so this whole area [he points to the area below his ears] was bald. But I though, thank God I have three weeks before we shoot. Still, when I got to the set, they were like, did you just get your hair cut? And I said, nope, I got it cut a few weeks ago. They filled it in, though. [My hair] varied throughout the film, because at the beginning his hair is very neatly kept, but as it goes on we wanted him to degrade. Toward the end it's all messed up and he has the circles under his eyes.

One of the best details is how well Oswald's post-beating droopy eye is recreated. Was that make-up trickery?

It was a piece of gelatin! My girl Ashley in make-up, man, every single day she put it on there, and it looks exactly like him.

What's remarkable about your performance is you capture this narcissistic aspect to Oswald. The best scene has to be when he's addressing a field of reporters but we realize he's just talking to himself. 

He had a very grandiose attitude. He wanted to be noticed, he wanted to be seen. He wanted to say, I've arrived. That scene was really fun, because we shot the bits from one side that were close on me, and we had an electrician standing at the window with a flag and he had this big, old, bright light that was blocked out so it looked like I was in a dark room, then, when Marina comes in he just took the flag out of the way so you see it's just the wall. That wall was a dummy wall and put reporters back there. 

And then, at the end right before he's shot, he's finally getting that paparazzi moment he always wanted. 

He'd arrived; he was there. Like he says, "I thought there were gonna be reporters," and finally there were. 

How difficult is it to play a real person as opposed to a fictional character? 

There is more responsibility. A fictional character you can make it however you want to make it, and just ask the director where he wants to take it. Because there are so many people who are going to watch this and say, eh, I don't know about that, that's not right, you want to get it right. You've got to get it on point. I would say I feel a personal responsibility to make it right.

This was a showstopper performance. It's much too early to discuss these things, but I'll ask you anyway -- how would  you feel about awards buzz, were it to happen?

I don't care. I've been doing this for over 20 years and I come from a family of it. I just have fun. This is something completely new to me, this junket thing. I love people and I love talking to people and just human interaction. You've seen me, I give hugs to everybody. I'm a hugger, I love that human connection. I don't care. If it happens, it happens. But I'm not after it. I don't care. I mean, fine, I'll take it, but it's more about the work and I have a blast on set. It's so much fun. Especially with a movie, it's a family, and I give hugs to everybody. Everybody on set, I hug, every morning and at the end of the day when people are packing shit up, I'm like, give me a hug. I love that. That's what I prefer. When I was in Richmond, our script supervisor Rachel, very quiet, I gave her a hug at the end of shooting one day and she said, I have to tell you, this is my favorite part of the day. That's my favorite thing. To me, it's more about human connection. 

You've mentioned that your parents were Kennedy freaks. Maybe I shouldn't say freaks...

No, freaks is fine. 

But they must have been excited about you landing this role. 

They were freaking out. They're both actors, too, and they were just over the moon about it. Oh my God, I'm so proud of you! 

Obviously you didn't have scenes with Rob Lowe or Ginnifer Goodwin, but did you get to see them in action? 

When I first got to Richmond, they were just finishing up the tail end of their stuff, so I  had a few days off. I was walking around town, exploring, researching, meeting people, and I'd have to go in on set for an interview. I would watch the monitors and watch them work.

Was that helpful to you?  

I'm not sure where the split happened, but Marina and Lee both loved Kennedy, and when [their] baby Patrick died, they felt a personal loss, which is crazy, right? At the end of the day, Lee wanted some attention. It was gonna be Walter, and when it wasn't Walter, it was Nixon. When it wasn't Nixon, it was Kennedy. It definitely tied into in a certain way. I was more blown away by watching Rob and Ginny do their thing. Jack as well, the three of them together was amazing.

How has being on this trip to Dallas and seeing all of these important locations -- Oswald's apartment, his tombstone, the theater where he was arrested, the location where he was killed -- been for you? 

I don't know, I feel refreshed and reflective. Just going around to all these spots today was like taking a deep, satisfying breath. Everybody was like did you go on a pilgrimage to Dallas before you began work, and the fact is I hadn't been for many, many years. Now, after today, I'm really glad I didn't. Now that all is said and done and the work is done, seeing all these places and being here is more of a reward than anything else. 

What's next for you? 

I'm a regular on a new Fox series called "Wild Blue," produced and created by the boys who did "Justified," picked up for 13 episodes. We haven't even shot the pilot. We go to North Carolina in March 2014. I'm in movie mode, though, so I would love to line up a couple more things before I go to do that. 

You have an awesome calling card for that. 

Hope so! We'll see!

But what's something you'd like to do, movie-wise? 

I don't know. I would love to do a good gritty drama, a romantic role. I tend to play bad guys for some reason.

But you're a hugger!

I know, I'm a hugger! I don't know what the deal is! You're a psychotic, but I want to hug you anyway! I don't get it.