After Brianna Dension vanished from the house on Mackay Court in the early hours of Jan. 20, Reno police quickly realized they had an abduction case on their hands.

There was the blood on the pillow and tests proved it belonged to Brianna.

They also found DNA of an unknown man at the scene.

But there were no witnesses. No scent of Brianna outside the house. And all her things were still inside. KRNV-TV crime reporter Victoria Campbell.

Victoria Campbell: So of course the implication was she had not left the house under her own power. Perhaps she had been carried out. Why would she have been carried out? People started to assume the worst.

Search teams canvassed nearby neighborhoods and fanned out to canyons, fields and rivers.

Victoria Campbell: I think one of the most chilling things I saw was the police and public works officials lifting all of the manhole covers and checking all of the sewers to see if this young lady, right out in front of that house, had been thrown down a sewer.

Pictures of Brianna went up all over town along with ribbons -- in blue, her favorite color.

Victoria Campbell: The family set up a command post at a local casino. And that's when we saw hundreds of people coming forward in this community and volunteering to search.

Jennifer Bushman: We are the biggest little town in the world. It's up to us to find her.

By this time, the city of Reno had all but adopted Brianna Denison. Reporter Jaclyn O’Malley.

Jaclyn O’Malley: You know, everybody just kind of says if that was my daughter, if that was my sister, my friend, I would want you to be looking for her too.

Early on, police had one potential suspect.

Holladay: That is our person of interest, it's somebody we need to talk to.

Remember the man who drove Jessica back to KT’s home the night of the abduction? The total stranger she flagged down?

Investigators released an image of his vehicle and urged him to come forward. They had questions for him.

Lt. McDonald: We had an individual that's unknown to these women that was -- had drove one of them home to the residence. Could have come back and certainly abducted Brianna.

But within days the man did contact police. He was cleared.

Victoria Campbell: When they ruled him out , they had to start looking elsewhere.

But Reno police were working another theory of the case: that this was no isolated incident, that Brianna’s abduction was the work of a criminal they were already looking for. It’s a man who police believed had committed two earlier assaults against college students.

On Nov. 13 , two months before Bri vanished, a 21-year-old woman in an off-campus parking lot was grabbed from behind and groped.

Lt. McDonald: Put his arm around her and knocked her to the ground. Told her not to scream. And of course, she did scream. So he jumped up and fled.

But police believe he dropped something as he ran: condoms.

Lt. McDonald: They were clean. They were pristine. And they were not in a box. So that indicated to us, you know, they were probably dropped by the suspect.

One month later, on Dec. 16, there was another assault. This one was more serious. A 22-year-old foreign exchange student was attacked outside her home in the early morning hours. Once again, the attacker came at his victim from behind.

Lt. McDonald: Arm across the chest from one arm, and then the other hand cupped to her nose and her mouth. She went unconscious shortly after that, most likely from being smothered . The next thing she remembers is coming to in a vehicle.

The woman was driven a short distance, and then she was sexually assaulted inside the car.

Lt. McDonald: During the assault, she was  told not to look at the suspect. When the assault was over, she was brought back to her residence and told to get out of the car and not look back.

She never did see his face, but even so the woman gave police a lot of information. Her attacker was a white male, with tanned arms and soft hair on his chin. No body odor. No accent. And that wasn't all.

Victoria Campbell: She said that his pubic hair had been shaved. And that's what they have to go on still. Is the help that she provided from that terrible experience.

The woman also gave police a detailed description of the suspect's vehicle. It had a step underneath the passenger side .. So police concluded it was a pickup truck or an SUV. Inside: a radio with distinctive red and blue lights. And this intriguing tidbit -- on the floorboards was baby shoe. But even more important was something else the woman gave the police -- her attacker's DNA.

Lt. McDonald: The lab started working real hard at that point trying to you know analyze all the DNA evidence that was in those cases.

Days after Brianna disappeared, investigators caught a huge break. They learned that DNA from both of the earlier attacks was a match with the DNA found at the house where Brianna vanished. Meaning that police were now looking for a serial sex offender.

Cmdr. Struffert: The DNA evidence from the scene of Brianna’s abduction has been linked to DNA evidence from an abduction and sexual assault that occurred nearby.

For Brianna’s family, it was devastating.

John Zunino (Brianna’s uncle): I mean, it was clear that this was a rapist now that had Brianna … and that was like a big sock in the stomach. It took our breath away, all of us.

And there was more.

Police believe another incident is linked to Brianna’s case: 24 hours before she was abducted, they say the same man attempted a break-in at the home of the foreign exchange student, his second victim.

Lt. McDonald: She was awakened by somebody at the back door, trying to gain entry. So much so, with so much force, that the door was actually bowed out, and the doorknob was damaged and had to be replaced.

Victoria Campbell: And that's when we knew there was someone out there who was making this a habit.

Reno police were now running the biggest manhunt in city history. And perhaps the most chilling aspect to all of it? Every one of these attacks -- including Brianna’s abduction -- took place within a four-block radius. This was a predator who knew his turf.

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