Stan Romanek says he encountered his first UFO on the outskirts of Denver almost eight years ago.
"It was just after dark," he said. "And I looked up and there was this big red blue looking UFO."
In 2000, Romanek's video camera caught a shaky bright light in the sky. Others in the park that same night say they witnessed it too and the video made it onto the local news.
But that was only the beginning for Romanek, 46, who belongs to a growing community of believers who say they have been personally touched by extraterrestrials. Since then, Romanek says he has been abducted by other forms of life.
"What they are? I couldn't tell you. Are they from a different planet? I can't tell you. I know they're not human, whatever they are," he told ABC News. "But as far as I'm concerned, they're not from here."
Romanek captured the alleged sightings of extraterrestrials on video and showed "Primetime" the evidence of his contact with extraterrestrials.
Romanek Claims to Witness Paranormal Phenomena
Romanek said his first UFO sighting occurred in broad daylight, while he was driving his car near Denver's red rocks amphitheater in September 2001. Afterwards, he said, he began seeing UFOs all the time and could barely look up without seeing some strange light or "orb" in the sky.
"If you're a true experiencer, true abductee, you have what's called high strangeness," Romanek said. "All these weird, bizarre paranormal things start to happen, almost like your house is ... being haunted."
Over the years, Romanek claims his wristwatch stopped working, lights would flicker at his mere presence, and birds would crash into his car.
"It's almost like they're chasing me," he told ABC News. "Maybe I'm the story, for whatever reason, they're harassing me and I can't tell you why. ... I have no answer to that. Even now, eight years later, I have no answer for you. I can't tell, you know, why me."
He claims that one night aliens came knocking on his door at 2:30 in the morning and woke him up.
"Three creatures -- beings -- came to the door, I, honestly I thought it was somebody in a mask. I thought they were going to rob us," Romanek said. "As I got closer, I started wondering if they were masks because I could see the veins in their head, I could see their facial movements. I could see their mouth move. I could see their eyes blink. And as I got really close, that when I realized that this is something different. And I started to get frightened."
Romanek told ABC News that the female being led him out of his second-story apartment onto the balcony. He recalled feeling a "tap" on the back of his head and waking up in a room in an unknown location, surrounded by a bizarre light. There, he said remembers being on a table, in severe pain.
Romanek said the beings communicated with him telepathically, filling his mind with unexplained and often apocalyptic images.
"Images of this horrible catastrophe, you know, wind so strong it's scouring the pavement off the earth, forests burning, devastation of the planet," he said. "And when it was over, I'm going, when is this going to happen? When's this going to happen? Because, I was pretty much in tears by this point. I was so terrified."
He said he is convinced the aliens were trying to send him a message.
"A lot of people won't believe this because of fear, a lot of people won't believe this because they won't, don't want their little, you know, version of reality altered. But I know what I've gone through," he said. "It's like, am I crazy? I've got to be crazy, I hope I'm crazy because maybe I can get help. But every time I think that, something else happens to prove that I'm not crazy."
Investigating Romanek's Story: 'Physical Proof'
UFO investigator Chuck Zukowski, who has dealt with thousands of claims of UFO sightings for nearly 25 years, said Romanek represents a small minority of those who've experienced things that defy explanation.
"About 90 percent of the stuff that I see, that comes in to me can be explained. It's the 10 percent and that 10 percent means that I have to go out there physically, look at what they saw, talk to people in person and out of that 10 percent, you may get 2 or 3 percent which is a total unknown," he said.
Zukowski said he has spent countless hours conducting his own investigation of Romanek's videos and documentation and said it is clear that something physical is happening to Romanek.
An x-ray shows the presence of an implant in Romanek's leg, which he says appeared after an alien abduction. When ABC News asked for an independent medical assessment of the implant, Romanek said it suddenly disappeared.
Romanek showed "Primetime" photos of puncture marks on his legs, which he claims were the result of "alien testing" and could not have been self-inflicted.
"I'll wake up, not know anything happened, and I'll have puncture marks, and they're usually in triangles, the ones that I get, perfect triangles," he said. "I found some on my back, didn't even know I had them."
Romanek also told ABC news that his camera went missing for a few of days, and when he found it again, photos of aliens appeared mixed in with his other photos.
"I don't know how they got there, but they were there when we had downloaded pictures off our camera," he told ABC News. "To me they look real. I mean there's so much detail in them. I don't know how they got on my camera but they look like E.T.s."
Zukowski told ABC News that Romanek's story and markings are consistent that of other abductees' stories.
"A lot of things that's happened to him, including the implants and where the implants were placed are common with other abduction, [or] ... I should say scenarios," Zukowski said.
But skeptics argue that Romanek and others like him are just seeing what they want to see.
Married to an Abductee: Stan Romanek's Wife Speaks Out
Lisa, Romanek's wife of seven years, has also become a believer. She said she is "absolutely sure" that her husband is being visited by aliens.
"I've been there and lived it with him. There's no doubt in my mind that what he is saying is real, is true," she told ABC News.
Raising their three children outside of Denver, Lisa Romanek, 40, said that for the past eight years her family has endured the unexplainable.
"A lot of things, we try very hard to look for what other reasons could explain it," she said. "But when like all your remotes in your house disappear for three days and you have searched everywhere, and then you wake up the next morning and they're all lined up on the counter, that's something I can't explain when I've searched for them."
She doesn't just blindly follow her husband's whims, she said.
"I question everything. Stan questions everything. Just because we see it happen doesn't mean we're not intelligent enough to think someone might be doing things," she said. "But who in the world's going to do it for eight years non-stop just to make us look like idiots?"
For the Romanek family, the real ridicule began after he appeared on "Larry King Live" in 2003, claiming to have captured an alien on tape.
Romanek said he shot video of an alien he named "Boo," who appeared at his kitchen window. Images of the alien in the video sparked a firestorm of controversy on the Web, with many expressing doubts about its authenticity.
But for the Romanek family, the mockery is no laughing matter. Lisa Romanek said her husband had to be hospitalized after he was physically assaulted by strangers on the street.
"He had a broken nose, broken wrist, he had a cut above his forehead here and down his cheek ... where they glued him back together, instead of putting stitches in," she said.
She said there is a good reason why she has stuck by him, even though she and her family have been taunted and ridiculed.
"Because I believe in what he is saying. I have seen. I know what he is saying is true," Lisa Romanek said. "And I have said it many times to other people that have asked me that question: I am not going to just abandon him because people don't believe it."
Inside Romanek's Hypnotic Regression Therapy
Under the guidance of psychologist Leo Sprinkle, Romanek uses hypnotic regression therapy to jog his memory about what he said were alien abductions.
"It's dark, but there's a weird light. A strange light and they're watching me. Oh, no. it's happened again. I've been taken again," he told Sprinkle during a session.
Sprinkle has encouraged Romanek to explore his memories, forcing him to work through the pain of the experience to achieve emotional revelations.
During the sessions, Romanek, a former computer repair technician now on disability who told ABC News he is severely dyslexic and only had only a fifth grade math proficiency, wrote high-order math equations with his eyes closed.
The equations appear to be known in scientific circles as "Drake's equation" -- a complex astrophysics' formula that approximates the number of planets in the Milky Way that might have intelligent life. Romanek claimed not to have any understanding of the equations.
"What's interesting, when I wrote it under hypnotic regression, I put times a hundred ... which may be the ETs or whatever are telling us, there's more out there than we think," he explained.
But Harvard University psychology researchers Susan Clancy and Richard McNally contend that hypnosis is not a truth serum. They said hypnotic regression can often help conjure up vivid, but distorted false memories, leaving many people who undergo the procedure feeling even more isolated.
"Some of these people go to hypnotic regression therapist, specializing in alien abduction phenomenon," McNally said. "The therapist would then take the person back to that moment where they were lying paralyzed on the bed. ... So it seems like memory is surfacing. And so then what you find with this type of leading question, this type of probing questions, is you get this narrative of this detailed kidnapping experience where they're taken to space ship and strapped to a table."
Sprinkle, Romanek's psychologist, who said he believes in the existence of aliens, was asked to leave his position at the University of Wyoming after 25 years there.
"There were some people who saw my work as unscientific, and unprofessional," Sprinkle told ABC News.
Multiple studies have shown that those who believe they've been abducted by aliens are no more likely to suffer from psychiatric disorders than the rest of the population.
But experts say that stories about aliens and spaceships that powerfully resonate today on film or in the media can become easily ingrained in our subconscious and then vividly re-enacted in our dreams, resulting in a common disorder called sleep paralysis.
Sleep paralysis, the feeling of being awake but unable to move during sleep, is quite common, according to experts. Sufferers say they feel as if they're totally paralyzed -- a symptom that parallels what many abductees describe during their experiences with alleged extraterrestrial life.
"What tends to be similar is they come in the night, they take you some place, you're in a spaceship," Clancy said. "The aliens tend to look the same, which is that sort of greenish, triangular head, big eyes and they perform medical or sexual experiments on you."
Personality Profile of Alleged Alien Abductee
According to McNally, sleep paralysis is one part of a common personality profile for alleged alien abductees, along with a strong imagination.
"The person has to entertain the possibility that aliens are coming to earth and kidnapping individuals. They score high on absorption; they have powerful, fantasy and imagery capabilities. A third thing is they're acquainted with the cultural narrative of alien abduction," McNally said.
"And then you have the issues of isolated sleep paralysis, where the person wakes up in the middle of the night, they, have hallucinations," he said. "Then most of them go to a therapist who studies the alien abduction phenomena."
Clancy said she has experienced sleep paralysis and knows how real it can feel. So it pains her, she said, to tell people who believe they have been abducted by aliens that it is all in their imagination.
"It does because I can imagine every alien abductee out there saying, 'This terrible person. You know, how can you say it didn't happen?'" she said. "But I want to say that, you know, the human memory system is very fallible."
In the end, alien abduction may be as much an exploration of the inner-workings of the human mind as it is the outer reaches of the universe. Psychologists say we will always be intrigued with the possibility of the unknown.