"The terrible tragedy at Parkland had a profound impact on those students, their families, our nation and me personally."
O'Connell interviewed Bowie in 2002, and he now shares his insights about Bowie and how his book on Bowie's literary influences came into being.
Their five-year study found many similarities between the thrill-seeking and sometimes inexplicable-seeming choices of teens and those of adolescent animals developing in the wild.
Walker opens up about his new book, 'The Art of Noticing,' and innovation in the digital age.
"He failed as the moral leader of our country that day. He came out of the closet and showed us who he truly is, a racist, plain and simple."