Good evening. I'm David Muir. And I'm Elizabeth vargas. A honk of a horn turned a night into a nightmare. For the first time, the people that were right there are now reliving it for "20/20." But as... See More
Good evening. I'm David Muir. And I'm Elizabeth vargas. A honk of a horn turned a night into a nightmare. For the first time, the people that were right there are now reliving it for "20/20." But as we come up on the one-year anniversary, the question remains. Was road rage really the cause? Here's Debra Roberts. Reporter: It's a cool Thursday night in America's favorite adult playground, las Vegas. And the strip is already jumping. But across town, near another playground, in a part of Vegas where people actually live, a local mom is about to put tonight's mystery in gear. 44-year-old tammy myers is giving her daughter her first driving lesson. At 10:00 P.M. At night? I wanted to go at night, because there's no cars around you could hit. Reporter: Why did you pick that area? It's close to home. Reporter: So, they go to this empty parking lot at a nearby high school. Tammy and husband bob have raised four kids in this neighborhood. We live in Las Vegas. It's a 24-hour town. Reporter: Bob is on business in California, a traveling vendor, selling hats and t-shirts at fairs and sporting events. Son Robert Jr. Is with him. The others, back in Vegas. The eldest, Brandon, at home. Here's how crystal says it played out. She takes the wheel, delicately maneuvering the car. Then the lesson moves from the parking lot to the neighborhood's main streets. We stopped and she pulled over, and we switched seats. Reporter: Tammy takes the wheel. She's going at a snail's pace, when suddenly, an impatient driver appears. A silver car, he's riding our bumper. I honk the horn. Reporter: That honk of the horn, something we've all done, would change everything. You pull up here. She turns right. And right about here -- Reporter: She says that silver car suddenly sideswipes them. Who is this guy? I didn't recognize them. Reporter: Were you scared? Yes, I was really scared. He gets out of the car. Reporter: It's okay. Take your time. He says I'm going to kill you and your daughter. Reporter: In a panic, crystal says they flee the scene. But what happens next is a puzzle we piece together tonight. Everyone agrees that sometime after 11:00 P.M., two cars go to the end of the cul-de-sac where the myers live. And a sedan, in hot pursuit with a gun. You heard the shots? Yes. Reporter: Did you know she had been hit? Yeah, I was screaming, mom's been shot. Reporter: Brandon remembers running to his mother's side as the sedan leaves the scene. I was screaming, mom, please stay here. Stay here. Everybody was telling her to stay awake, because she was closing her eyes. Reporter: She's hit in the head. Brandon dials 911, and at 11:34, tammy is rushed to the hospital. Did you have any idea who had shot your mom? No. All I saw was the gunfire. Reporter: Bob gets fragments from a distraught crystal. She said, there was blood everywhere, all over mom's head and face. Reporter: He drops everything, and begins driving home. How fast are you driving? 100 miles an hour. Reporter: Every thought saturated with concern for his wife. It's not until the early morning hours of February 13th, when bob gets a call from police. He says, Mr. Myers, it started off as a road rage, they followed your wife home and shot her. Reporter: He begins to call TV stations, asking for updates and granting interviews. I'm speechless. I've been with this woman 25 years. Reporter: He's now the vocal spokesperson for the myers family. He called our station and says, hey, I'm angry about this. How could someone do this? I didn't want to freeze out the media. You can't find killers without the media's help. Reporter: By daybreak, bob arrives and sees his wife's lifeless body. I see my wife. I said, I'm here, baby. And I said, it's going to be okay. You know? Reporter: But his optimism is quickly dashed. The main doctor says, she's not going to make it. I told my wife, no matter what it takes, I'll find out who did this to you. Reporter: Later this morning -- I'm right here. You know what you did. Come here. Reporter: He stands before cameras saying there was as many as three killers in the car. By the end of the day's news cycle, here's the official narrative. Police say three suspects nearly collided with her green buick. Reporter: As the buick becomes a makeshift memorial, tammy looks to be just another victim in a string of road range incidents. Most recently, in Austin, Texas, two men going at it with a baseball bat and a wooden pole. But a mom, cut down in her own driveway. But despite all the attention, no arrests. The next day, February 14th, a heartbreaking Valentine's day. Vegas police release the security video of the sedan cruising the neighborhood, and with it a composite sketch. They say it's crystal's description of one of the men. As far as we can tell, there was no prior contact, they're complete strangers. There's a manhunt, everyone is like, could this happen to me? Reporter: That night, an agonizing moment for bob myers. At 7:05 P.M., he disconnects his beloved wife from the respirator. She'll never leave my heart, but she's gone. I didn't want my baby to suffer. But I didn't want her to go either. Reporter: But you had to do it. Had to. Reporter: But before tammy can have a funeral, she's about to be buried. Tammy myers went looking for the driver. Are you happy? Reporter: As the story takes the first of what will be many sharp turns. Was the innocent victim really all that innocent? Maybe this isn't what I thought it was in the beginning. Reporter: And a young woman with inside knowledge, to break the case, she must find the courage to turn in a friend. You called the police. What did you say? Everything.
This transcript has been automatically generated and may not be 100% accurate.