Video Key in Texas Student Murder Case

The Murder of Melanie GoodwinCourtesy the Goodwin family
University of North Texas student Melanie Goodwin, 19, stopped at a convenience store to pick up a snack for her boyfriend ... and met a horrible fate.

Employees arriving at Trans-Tech software company in Carrollton, Texas, the morning of Sept. 25, 2007, were greeted by the unthinkable.

Police Det. Greg Fraid was the first investigator to arrive on the scene.

"The call is a burnt body in a ditch and the body is charred beyond recognition," Fraid told ABC News' Jim Avila in a recent interview. "We were afraid it might be a serial killing, just the way the body was laid out in the ditch, it almost looked like it was posed, with her legs facing the parking lot and her knees kind of up. You can only tell it's a female by her hair and the French fingernail tips that she's had done. I've seen my share of terrible things people do to each other, and this one is probably the most horrific I've ever seen."

VIDEO: Store cameras catch killer stalking victim, 19; later, he buys gas, burns body.Play

Police did not yet know that Melanie Goodwin, a sophomore communications major at the nearby University of North Texas, had gone missing the night before. They did not yet know that less than 12 hours earlier, Goodwin, 19, had stopped at a convenience store to pick up a snack for her boyfriend -- and encountered her terrible fate.

For part 1 of Melanie Goodwin's story, click HERE.

For all they did not yet know, police benefited from a crucial, immediate break in the case. The Trans-Tech parking lot was under round-the-clock video surveillance. Whatever happened to the young woman had happened on camera.

"You get excited, because you had a video which showed at an early morning hour a vehicle pulling up and somebody pulling the body out of the car, down to the ditch, back up to the car to get something out of the car, back down to where the body was, and you see a horrific burst of light, which is the flame and the body burning," Fraid said. "Person comes back up, jumps in the car and leaves."

Watch the full story on "Primetime" Wednesday at 10 p.m. ET

Police were able to identify the vehicle in the surveillance video: a red Saturn.

"I now have a vehicle I can look for," Fraid said of his thinking at the time. "There's an image which looks like a male. I've got a little bit of clothing that I can see from the video. You can see a white shirt, you can see half pants. Now you have hope that we can get a running start on something that we had nothing just a few moments ago."

Meanwhile, in a nearby suburb, Goodwin's boyfriend, Ale Valencia, was waking up in a panic. She hadn't arrived during the night as planned.

"I called and called and called and called," Valencia said. "I was trying to calm myself down, like you know, everything has to be OK. She's missing, missing -- and let's find her."

Convenience Store Murder: 'God Was With Me'

Hoping for an innocent explanation, Valencia held off calling the police.

Detectives, meanwhile, were working their newfound mystery in a vacuum. They had no missing persons report -- nothing that could help them put a name to their badly burned Jane Doe.

Their break came when an officer located the red Saturn. Detectives traced the license plate -- "Angels are watching over me," the plate bracket read -- to Glenn Goodwin, Melanie's mother.

When police arrived at Peggy Goodwin's home, they said, they knew they had found not a murder suspect but the victim. They told her about the body. She worriedly called Valencia, whose own worst fears deepened.

After submitting to interrogation, Valencia led police to Goodwin's last known location. She had called Valencia from the Quik Trip convenience store where she stopped shortly before 2 a.m. to pick up Cheetos and chocolate milk for him.

At the convenience store, the tale of the tape continued. Surveillance video showed a young man loitering. It showed Goodwin walk in. And it showed him following her out.

"It gives me a picture of a person that I can put on the news, I can point out to whomever and try to identify him," Fraid said. "There were things that were placed in front of us that we never thought we would see. Things were just falling in line. God was with me on this one."

The man was identified as Ernesto Reyes, 20. After he was filmed at the Quik Trip, Reyes was filmed at a closed Chevron station, where he tried unsuccessfully to buy gas. Police found that video, too. In the video, prosecutors said, Reyes can be seen noticing something on his shirt, which prosecutors would later claim was blood. Reyes took his shirt off and turned it inside-out.

On yet another tape, moments later, Reyes is seen again, at a nearby 7/11. There, he buys $1.76 worth of gasoline. He casually filled a gas can and asked a stranger to borrow his cell phone.

"He used the phone, he told him, 'God bless you, you know, have a good evening,'" Dallas county prosecutor Andrea Handley said. "And he calmly walked away, as nonchalant as can be. Cold-blooded."

The final videotape shows Reyes dragging Goodwin's body to be burned. Reyes' DNA would be found in her body.

The evidence against Reyes seemed overwhelming. But when the case came to trial this past February, a year-and-a-half after Melanie Goodwin was brutally murdered, Reyes' defense attorneys were quick to point out there were 90 minutes not recorded between the time Reyes followed her out of the store and when he is shown blowing her up.

An hour-and-a-half when, perhaps, the angels watching over Goodwin blinked.

Watch the full story on "Primetime" Wednesday at 10 p.m. ET

For part 1 of Melanie Goodwin's story, click HERE.

Visit the "Primetime" Web site Wednesday for part 3 of Melanie Goodwin's story.