It was Friday, Feb. 15. By lunch time, the weather had turned warm, and snow started melting in this field in southeast Reno.

A man who worked in the area decided to take a shortcut through here. He stumbled across a body.

Then he called police.

Lt. Robert McDonald’s mind was racing as he headed south of town.

Officers roped off the large vacant lot.

KRNV reporter Victoria Campbell was there.

Victoria Campbell: People started walking up, "Is that Brianna?” "I was on a search team. I've been looking for her. I hope it's not her.“

On the other side of the yellow tape, police were feeling the same way.

Lt. McDonald: We had a lot of concern, from the very beginning, that Brianna was probably not alive.

And as he looked down into that gully, McDonald had a bad feeling that everyone's worst fears had come true.

Lt. McDonald: I was 95 percent certain that who we were dealing with here was Brianna … I walked out of the field, and I just had my head down and the hope was finding had left. Detectives that were there, I could see the look on their face.

Lt. McDonald and another detective drove immediately to speak to Bridgette -- Brianna’s mother.

Josh Mankiewicz: The police tell you in that first conversation that they thought it was probably her?

Bridgette Denison: Yeah. And then I kept asking about her nose stone -- or because she doesn't have pierced ears. I asked if they could tell if there was no pierced -- and the scar on her ankle. And they just said the elements, they weren't able to tell. So we had to wait for DNA.

Brianna's childhood friend, Danielle Detomaso, remembers the moment she heard.

Danielle Detomaso: I just went completely blank. It was just so shocking. And then a couple of minutes pass, and I just broke down and I couldn't just stop crying and crying … and, like, "This isn't happening. This can't be real. This can't be the end. We're going to find her. No, this isn't her." And I couldn't accept it.

The next day, police made it official.

(Feb. 16 police press conference)

Deputy Chief Jim Johns, Reno police: An autopsy today has determined that the remains of that female discovered in the field are those of 19-year-old Brianna Denison … The official cause and manner of death was strangulation … It is a sexually motivated crime.

Bridgette Denison: And all I can say to that is at least I’m not waiting four years later wondering. That's about the only positive I can get out of it.

Investigators believe Brianna’s body had been lying in the field for at least a week.

Bridgette says police told her they believe Brianna was not abducted, at least not alive. They think she was killed inside the house at 1395 Mackay Court.

Bridgette Denison: They think that he strangled her right then and there. And it was a matter of seconds. And that's all I know. I didn't want any more details.

Now it was a search for a killer. The FBI and more than 40 detectives from the Reno police and surrounding area chased hundreds of leads.

But after three more weeks, still no arrest, and still no hits from that backlog of DNA at the county crime lab.

Then, on March 6, investigators released a detail they'd been holding back: that the man police were calling a serial sex offender had left a calling card when he dumped Brianna in that field.

Police announced that two pairs of women's underwear were found intertwined and left close to Brianna’s body.

One pair in pink belonged to a woman who lived in the house at 1395 Mackay Court, where Brianna spent her last night.

Cmdr. Leigha Struffert: This pink pair of underwear has the DNA of Brianna, the suspect, and of the known owner of the underwear.

The other pair was a distinctive black thong, size small, with the cartoon character the pink panther on it.

On this pair was the DNA of an unknown woman and another unknown man, but not, police said, DNA from the man who killed Brianna.

The significance of that isn't clear. But police said it was no accident, and that the underwear was put there for them to find. They were now saying that the suspect may have an underwear fetish.

Josh Mankiewicz: This is where her body was found.

Former FBI profiler Clint Van Zandt says that underwear found here, and the location of this field, may reveal more about her killer.

Remember, the field is southeast of downtown Reno -- about 10 miles away from where she was taken -- and where those other assaults occurred near the University of Nevada-Reno campus.

Clint Van Zandt: We're only a minute or two off the interstate. So what the police have to consider are probably one of two things. Either this is a location on his way home, where he lives, where he works, somewhere where he had to get to that night after he murdered Brianna. Or is he so sophisticated that he would come to the opposite end of town, dispose of the body, and then head 180 degrees the other direction?

Josh Mankiewicz: What about the theory that the guy may have left the area?

Clint Van Zandt: The smart money would perhaps say he would get out of this area, but if you do that, if you've got a job, if you've got family, somebody's going to raise your hand and say, "You're gone, you're missing." And then they're going to start to put-- "Let's see, he's gone. His truck looks like this.” So the other side says, "Does he just stay right here? Does he hunker down?” But unfortunately, he's the type of guy who’s going to be out. He's going to be hunting. He's going to be stalking.

And if that underwear found in this field was placed there by the killer and meant to be found by police, would there be more victims?

Josh Mankiewicz: What do you think? Is the guy going to re-offend?

Clint Van Zandt: Well, this is the challenge. Remember, there are some who say the underwear that was found out in this field -- that perhaps he put that there intentionally, trying to challenge police investigators.

If he did that, is he going to go out and try to find another victim? I mean, right in the face of the police, saying, "I’m doing this. Neither you nor this community can stop me."

But the police were doing everything they could to stop him. By the end of February -- working off a profile of the killer -- detectives came here to the "Moonlite Bunnyranch" -- a legal brothel about 30 miles south of Reno. They spoke to the owner, Dennis Hof.

Dennis Hof: The police asked me for help. There wasn't any question about it. And I said, "Let's talk to the girls. Let's talk to the girls and see if we can find somebody that fits that profile that-- that comes into the ranch."

One of the women who works at the Bunnyranch told the police about a regular client who seemed to fit the profile.

Dennis Hof: She was scared. He had tried to choke her a few times in a party.

Josh Mankiewicz: You mean during the session?

Dennis Hof: During the session.

More on the case City of Reno Web site on the case Bring Bri Justice: Blog by Brianna's family

At the request of detectives, the woman enticed the man back to the ranch, and this time, police were there, too: undercover.

Dennis Hof: When the customer came back the next session, the girl kept the condom and she kept the glass that he drank out of. And we turned that over to the police.

The DNA was rushed to the crime lab. But it was another dead end. No match.

And on March 13, the sheriff announced that they were done processing those thousands of samples of felons' DNA that had been sitting on the shelf at the county crime lab.

Michael Haley: That review of those samples did not end in a positive result of hitting on any major homicide case.

Translation? No match there either.

It's been more than two months since Brianna was taken. The tourists still come and go from the casinos, but for the residents of Reno, the questions and the pain won't go away.

The signs around town have changed. The search for Brianna is over. The search for her killer is not.

Victoria Campbell: People are angry. They're frustrated. And when they find this man, I think that this community is going to demand the harshest possible sentence for him.

The people of Reno have made a long journey from hope to sorrow to fear.

Victoria Campbell: We're watching our children. We're urging young people to be careful. This is not something that this city is accustomed to. This is a 24 hour town. And it's usually safe here.

But it won't be--- until Brianna’s killer is caught.

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