campaign event for congresswoman gabrielle giffords. eight people are killed. was anybody injured? did you say gabrielle giffords was hit? she s hit. she still has a pulse. reporter: the congresswoman was shot in the head but survives. she was lucky. when i saw the trajectory of where one hole was and the other was, i was like, my gosh. reporter: because it was so far apart? yeah. it went through a lot. reporter: three and a half months later, the first public steps in the congresswoman s remarkable recovery. in 2011 i tried to put a spotlight on big hits on the brain. trying to find evidence that football puts young people at risk and professional players as well. in february, david deweson committed suicide, and he left his brain to scientific research. when the findings came back, his brain had tell tale signs of chronic injury. as stories like this rolled in, the nfl tried to put in new rules to protect players. ah! reporter: then it was march. i witness