Transcript for Former baseball player's fight against ALS leads to Ice Bucket Challenge: Part 1
It began with a simple idea. Fill a bucket with water. Throw in some ice. And in the summer of 2014 -- the ice bucket challenge flooded the internet. From saintly Irish nuns. I accept the challenge. Reporter: To all manner of celebrities. More than 17 million people dumping ice water on their heads, helping bring massive attention to an otherwise obscure disease, A.L.S. Everybody on the street knew the term A.L.S. A.L.S. A.L.S. A.L.S. It suddenly had a real face to it. Reporter: With it raising over $220 million for charity. We've mobilized things that wouldn't have happened without the ice bucket challenge. Reporter: It wasn't Kermit or Oprah or even a future president who unleashed this phenomenon. It was a young athlete from suburban Massachusetts, Peter Frates. Swinging the bat today with an awful lot of confidence -- Reporter: The man behind the ice bucket. For a young guy like myself to be diagnosed, hopefully I can use my youth and networks that I'm part of to promote some awareness. Reporter: And the courage he showed back then is nothing compared to the courage he's showing now. As I was about to find out. Pete grew up like any other kid. Growing up outside Boston. Hitting pop flies with dad. I have a kid that I new was chosen to do something great. I've known it since he was a boy. ??? How old are you Peter ??? Reporter: In high school he was a three-sport star. Team captain of the football and hockey teams. But it was baseball that would become his life's passion. Going back is Frates -- Reporter: He went on to play center field for division I Boston college. Frates is the leading base stealer -- Reporter: Wearing his lucky number 3. Despite athletic month Wes, it was his personality that was larger than life. Pete's someone that puts out this infectious energy. He was friends with everybody. Reporter: Beloved by his hundreds of self-proclaimed best friends. When I first started dating him, he'd always be like, I'd like you to meet my best friend so-and-so. I was like, how many best friends do you have? Because I've met 14 best friends so far. Reporter: His many besties will tell you the strapping hometown hero was a hit on and off the baseball diamond. The addendum that my wife makes to every story is, he was the best-looking guy that ever walked on the Boston college campus. And when I remind her that I too went to Boston college, it makes for a couple of awkward moments. Reporter: His final year at B.C., Pete was named captain of the baseball team. During a grudge match against rival Harvard, he hit a monster home run in Fenway park. Who hits a home run at Fenway park, you know? It's kind of like every kid's dream. Reporter: After a short stint playing pro ball overseas, Pete came back to Boston to start a 9 to 5 job selling insurance, when he met the love of his life. What made you fall in love with Pete? He's very handsome, that didn't hurt. But from the beginning Pete was constantly taking care of me. Catering to my needs. As a girl it's very flattering. That's just the kind of guy he is. Reporter: Pete and Julie had just fallen in love. Dreams of marriage and children in their future. But just eight months after their started dating, Pete started feeling odd. Having trouble with simple tasks like buttoning his shirt. After a series of tests, doctors asked him to come in. And bring his parents. The doctor walked in. He went like this with his hand. He said, this is not the common cold. This is not Lyme disease. It's not Parkinson's. It's not M.S. I hate to tell you, Pete, Mr. And Mrs. Frates, you have A.L.S. Reporter: It was a death sentence. A.L.S., aim I don't trovic lateral sclerosis. More commonly known as Lou Gehrig's disease. The rare neurological condition affecting roughly 30,000 mostly older Americans, robbing patients of their movements, their voice, and eventually their ability to breathe, all while the mind stays alert. Nancy ran screaming out of that office. She knew exactly the magnitude of this thing. Devastated. I didn't know if I should run after her or stay with Pete. All of a sudden I was, you know, faced with the person I wanted to spend my whole life with -- being, you know, given a timeline. Reporter: A.L.S. Currently has no known cause or cure. Most patients live only three to five years on average. But almost immediately, rather than wallowing, the brawny baseball star started looking at the diagnosis as a dare. Pete says to the doctor, how much money do you need to cure this thing? She puts her hand on his knee and says, Pete -- I just said a billion. I don't have any knowledge, but I think a billion would make a big impact. Reporter: A billion-dollar challenge to cure his disease. An astronomical figure for sure, but that didn't deter Pete Frates. He said to her, I will get you a billion dollars and we'll reach Bill Gates. We're looking at each other. I was on the ground laughing, that's absurd. We're a middle class family, what are you talking about? Reporter: Pete became a man with a mission. You're young, you have your whole life in front of you, I'll understand if you leave? Yeah, it was a short conversation. I'm pretty sure I told him basically to shut up. I was like, we're not having this conversation. And he dropped it. Reporter: Rather than tearing them apart, Pete and Julie promised to spend the rest of their lives together. Knowing that you were going to get married, knowing that you were about to say, for richer or poorer, in sickness and in health, what went through your mind? Before we got married I was so nervous about the actual ceremony and saying those words. I thought, you know, I'm going to get so emotional. Mr. And Mrs. Peter Frates. All of a sudden I was empowered. Yeah, we are doing this, in sickness and health. And I'm not crying about it because this is the choice I've made. Reporter: Pete, always the fighter, by this time in a wheelchair, stood up to walk his wife down the aisle. It's still kind of like surreal to think about. Because he was pretty much always in a wheelchair at that point. What does that moment say about Pete? That he literally could make himself walk if he wants to. Reporter: It's now been nearly six years since Pete's diagnosis. But thanks to modern technology, with Julie by his side, he's already outlived the average life expectancy. What do you think of this disease? I hate it. It's an extremely cruel way for someone to live. You are literally trapped inside of your body. No one should have to live through that. Especially someone who, you know, otherwise thought he had his whole life ahead of him. He looks emotional to me. Yes, he is. Yeah. I think he agrees. Reporter: Though paralyzed, Pete can still feel his wife's touch. He communicates emotions through his eyes. But he also uses them to move a cursor. These are Pete's eyeballs. We try and get this arrow as much in the middle of this screen sidebar. Then his eyes somewhat in the middle of this box. So he's now controlling it? Yes. Reporter: And he's very active on Twitter. Oh, look. He's tweeting at me. Reporter: It's those same social media skills that helped launch a million buckets. It was two and a half years into his diagnosis. I was watching videos of the silly friends doing the funniest thins and he was laughing hysterically. Reporter: So he challenged his hundreds of best friends, plugging into a network of athletes with massive social media followings. He right away was tagging people. Tagging people that he knew of influence. I accept the ice bucket challenge. Reporter: Almost instantly big-name athletes stepped up to the plate. Boston college alum Matt Ryan of the Atlanta falcons. Julian Edelman of the patriots. Holy smokes, that person did it, this person did it. The next thing you know your whole news feed is ice bucket challenge. When did it blow your mind? Bill Gates. Reporter: Pete's prediction came true. The world's richest man, perhaps the most powerful philanthropist, shivering for Pete's cause. And that billion-dollar prediction? They were almost one-quarter of the way there in just six weeks. But as the science of A.L.S. Progressed, Pete's body continued to decline. Just this summer, a crisis. Pete suddenly back in the hospital, reportedly at death's door. When we come back, Pete Frates battles back from the brink. And you're about to meet this inspirational young man who may soon benefit from Pete's tenacity.
This transcript has been automatically generated and may not be 100% accurate.