NEW : ` ` The worst scene I 've ever seen , '' FBI agent testifies . Agent recounts the `` chaotic '' scene of the 2009 killings at Fort Hood . Army psychiatrist Maj. CNN 's Matt Smith contributed to this report . Nidal Hasan opened fire on fellow soldiers in a crowded cafeteria and then killed 13 people before taking his own life. " Hasan has admitted he was the gunman ; he 's representing himself .
NEW : ` ` The worst scene I 've ever seen , '' FBI agent testifies . Agent recounts the `` chaotic '' scene of the 2009 killings at Fort Hood . Army psychiatrist Maj. Nidal Hasan opened fire on fellow soldiers in a crowded cafeteria and then killed 13 people before taking his own life. " Hasan has admitted he was the gunman ; he 's representing himself .