Tonight on Dateline, Angela went out for a bike ride around Dusk. She never came back.

We thought it was someone she knew at the time. She was living with? A boyfriend, yeah.

Then details started coming. It was surreal. What did you find out about the zombie hunter?

That really caught our attention. It said zombie hunter on the vehicle. The zombie hunter car.

The zombie hunter car, yeah, with the dummy in the back. Yeah, they're everything. They're bars, handcuffs.

17-year-old Melanie was riding her bike. She was later found floating in the canal.

The way she was killed just traumatizes you.

There is a madman on the loose. I thought we would never know who did this.

Everybody wanted to find this guy.

Just either of you think that there are more murders that we don't know about, I do.

The FBI profile said killer would not stop.

The zombie hunter, it sounds like a Halloween costume, but was this one worn by a killer?

I'm Lester Holt, and this is Dateline.

Here's Keith Morrison with on the hunt for the zombie hunter.

It was a Sunday evening in November, Phoenix, Arizona. A wash of cool air, finally,

as the sun dropped behind the valley's mountains. She loved this time alone,

as she peddled the long path by the canal that snaked through the city, and out along the valley floor.

She could think on her bike, prepare.

But of course we can't really know what she was thinking.

Can only imagine all these years later, can only remember.

That has burned into my brain. I'll never, ever forget that.

No, not that horror.

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