May 14, 2009— -- Darlene Ewalt of Harrisburg, Pa., was sitting on her patio at 2 a.m., talking on the phone to a friend about an upcoming cruise. She did not know it, but on that hot summer night of July 13, 2007, she was being watched, hunted.
Then, out of the darkness, came an assailant wielding a long knife.
As Darlene's husband slept upstairs, the killer slit Darlene Ewalt's throat, and stabbed her so violently she died in minutes.
"She screamed, 'Oh my God, Oh my God,'" her husband Todd said.
Darlene's family was devastated.
"I don't go outside alone anymore at night," her 21-year-old daughter Nicole Ewalt said.
Nick Ewalt, 24, said he is also haunted by the tragic memory of his mother's death.
"A lot of nights I don't go to bed, I don't sleep," he said. "I just lie in bed thinking about all that happened."
Darlene Ewalt's husband, Todd, said the murder of his wife "devastated my life. I've never felt anything close to that. I felt like someone ripped my heart out of my chest."
The agency believes the man charged with murdering Darlene Ewalt is just one of hundreds of killers who may have gone on similar killing sprees undetected along the nation's interstates.
Police believe Darlene Ewalt's killer calmly walked back to his rig parked at a nearby truck stop and drove away, leaving the crime in his rearview mirror.
Four days after Ewalt was killed, a York, Pa., woman narrowly escaped a shadowy figure slashing at her neck as she was startled out of sleep on her couch.
But 11 days later, on July 28, 2007, in Bloomsbury, N.J., 38-year-old Monica Massaro would not be so lucky.
Around midnight, the killer pulled into a truck stop near her home. He hid in the shadows, moving silently down the picturesque streets in the middle of the night, looking for unlocked doors.
Detective Sgt. Geoffrey Noble of the New Jersey State Police told "Nightline" what happened at the scene of the crime.
"He walks up these front steps and this front door, the door was unlocked, and he walked right in through her front door," Noble said. "He went through her house. He spent time in her house. At some point he ends up in her bedroom on the first floor."
Massaro Dies Alone
According to the police investigation, Massaro was sleeping in her bed when the killer came into her bedroom, but while he was there she woke up. She turned on her light and he attacked her with a knife, police said.
"The first significant wound was a cut to her throat, a fatal wound," Noble said. "The severity of the wound was such that she bled out and died very quickly. After her death, he continued to stab her multiple times."
The killer returned to his truck and left town, not leaving a trace of evidence linking him to the scene, Noble said.
"She died alone in the hands of this monster," he said. "She didn't have time to call for help or run. She was cornered. She had nowhere to go."
Less than 24 hours later, more horror began to unfold in Chelmsford, Mass.
At around 11 p.m. on July 29, 2007, a woman in an apartment complex there saw a man hiding in the bushes and called police. When officers arrived, the man had disappeared.
But a few hours later, Chelmsford police received a frantic 911 call. A man was trying to get into a woman's home in a trailer park.
Kathy Crowley said her daughter thought she saw someone staring into their home, so she went outside to see if anyone was there. She found a man dressed all in black, wearing a mask.
"Looked like a ninja," Crowley said. "Turned and look at me; just wasn't right. He followed me back. Banging on the door. I was totally freaked out. How could this be happening?"
The police arrived in minutes, but again the suspect had vanished.
Ninety minutes later, at 4:30 a.m., police believe the same man showed up at Kevin and Jeannie McDonough's house about a mile or two from the trailer park.
While the couple was asleep, their 15-year-old daughter, Shea, was woken up by a masked man standing over her with one hand over her mouth and a knife in the other.
Shea's crying and other noises woke her parents, who came running to see what was wrong. Kevin McDonough was able to overpower the attacker and Shea called 911.
"He's big he's like a big guy," Shea told police dispatchers in the call. "He is in my room, he came into my room and held, he put his hand over my mouth and held a knife to my throat and told me if I screamed he'll kill me. … My dad is holding him down, my parents, until you guys come."
Fighting for Survival
"She was told not to make any sounds, she began to whimper and cry. Fortunately her parents were in the next bedroom, the adjacent bedroom," Chelmsford police Det. George Tyros said. "And they heard the whimpers and cries and a few other noises coming from her room, they immediately jumped up and ran to her aid."
"We were just fighting for our survival that night," Jeannie McDonough said.
When police arrived, they found the intruder being held down by Shea's parents,. When they pulled off his mask, they found Adam Leroy Lane, a truck driver from North Carolina.
Evidence found at the scene even scared the police.
"There were a couple of knives, large hunting knives, and there was a fanny pack belt that had the knife sheathes hanging from it," Tyros said. "There was choking wire, a Chinese throwing star, and there was a leather mask with the eyes cut out and the mouth cut out, just a horrifying leather mask."
What police found in Lane's truck stunned them even more. They found what appeared to be trophies from past victims and a videotape.
"He had several DVDs, one of them was actually inside his DVD player, which was titled 'Hunting Humans,'" Tyros said. "This DVD is a story of a serial killer that hunts humans."
The killer in the video hunted his victims with a knife.
As he handled the case, Tyros decided to contact the FBI, which kept a database of 80,000 unsolved, apparently random, violent crimes from across the country called the Violent Criminal Apprehension Program, or ViCAP.
The FBI has recently started collecting information about serial killings and assaults happening along the nation's major highways. There have been 500 such murders over the last 30 years, and the FBI worries there are many more cases out there that have not been brought to their attention.
"We were surprised at the number of bodies," said Supervisory Special Agent Mike Harrigan, who heads ViCAP. "When we look at the highway, the highways in particular, and saw 500 out there. That causes some concern, and we think there's many more that just need to be put into our database that just aren't identified yet."
Roughly 200 suspects have been identified, and the overwhelming majority are truckers, he said.
Most of the cases involve truckers picking up young women at rest stops, killing them and burying their bodies hundreds of miles away from where they were murdered.
The FBI's program helps police with baffling, unsolved crimes to link cases that are sometimes half a country away.
Adam Lane: The Missing Link
"It seems to me sometimes suspects are using the distance as a smoke screen to cover their trail," Harrigan said. "When they are dumping a body and getting two or three states away, it gives them a comfort, or maybe a security that it will be difficult to identify them.
"The first thing we do when a case comes in, we look for specific characteristics of the case that we can search on. Let's say that the person was strangled," Harrigan said. "The search would run and it would pull up all the cases."
While prostitutes are often the victims, the Adam Lane story proves that is not always the case.
After getting calls from police in Massachusetts and New Jersey about unsolved stabbing cases, an FBI analyst determined they were shockingly similar, and both weren't far from major highways. The FBI analyst suggested that the detectives in those two locations talk.
After learning that Lane, who was eventually convicted of attempted murder in the attack on Shea McDonough, had attacked a girl in Massachusetts near a truck stop, Noble discovered that Lane was in Bloomsbury on the night of Monica Massaro's death, at a truck stop less than a mile from her home.
He decided to drive up to Massachusetts to confront Lane about Massaro's killing. The interview was videotaped.
During the questioning, Lane confessed to killing Massaro, but he spoke about the murder in a way that Noble will never forget.
"He described those events in detail without any kind of remorse, with callousness," Noble said.
And police had more than Lane's confession. One of the knives recovered in Massachusetts had blood on it. DNA analysis proved it was Massaro's. He eventually pleaded guilty to the murder.
Police in Pennsylvania say Darlene Ewalt's blood is on one of the knives Massachusetts police found when they arrested Lane. In that case, Lane is awaiting trial, charged with her murder.
Her husband just wishes he could have saved her.
"I wish I could have been there. I wish I could have stopped it," he said. "We were just short of our 23rd wedding anniversary."