Three witnesses contacted by The Miami Herald say they saw or heard the moments before and after the Miami Gardens teenager’s killing. All three said they heard the last howl for help from a despondent boy, and believe the sequence of sounds shatters the notion that Trayvon was killed in self defense. As the controversy grows, so does the number of voices disputing the official version that watch captain George Zimmerman gave to police: that the 6-foot, 3-inch, 140-pound teen assaulted him when Zimmerman, 28, tried to question him.