NARRATION: The shooting at Columbine High School happened 20 years ago. Sean Graves was a freshman.

SEAN GRAVES: I went to school. I went to lunch with my friends and we usually would hang out in the commons. But for whatever reason, I forgot my wallet, the three of us decided not to eat lunch that day, which prompted us to go for a walk outside because it was a gorgeous day. And by doing so, we ended up inadvertently walking out to witness both Eric and Dylan, they were loading what we called realistic looking paintball guns, but thats when they ratcheted off a few rounds and we realized that this is something completely different. My friend was murdered. And I watched the attempted murder of my other friend. And clearly, I was in the middle of it. They were trying to kill me, too.

NARRATION: Graves was shot four times while running inside for cover, where he was shot again.

SEAN GRAVES: I ran clear around the fence and, with my backpack still on, I managed to get my entire body behind a concrete wall with my hand on the doorknob to get back into the commons. And just that little bit of my backpack sticking out was enough for a stray bullet to enter the side of my backpack, enter my spine paralyzing me from the waist down and shooting out my hip. Im laying there in glass and I just remember I started praying.

NARRATION: Graves was left paralyzed from the waist down.

SEAN GRAVES: In the hospital I was told I would never walk again without support or crutches. And that wasnt good enough for me, so I spent the next three-and-a-half years going through high school, learning to walk again. And in order for me to do that, I literally had to crawl before I could walk. I managed to fulfill my own goal to walk across the stage to receive my diploma. And I walked out of there and I havent used the wheelchair since.

Because of my experience from this, Im more in tune with my surroundings. I walk into a room and I can tell you where the exits are. And if theres a crowd, I immediately pick out who could be a potential threat. I dont consider it to be a weakness, I consider it to be a tool that Ive picked up along the way that might save my life someday. I dont know.

I could spend my entire life living in fear, wondering whens the next attack or whens the next person going to do that, but that would be it. Id be living in fear. I would be giving in to what they wanted to happen.