Sitting in a wheelchair, his voice soft but unwavering, U.S. Army psychiatrist Nidal Malik Hasan took responsibility Tuesday for the 2009 mass shooting at Fort Hood.

¡°Fellow members, good morning,¡± Hasan began at the opening of his court-martial at the army post in central Texas. ¡°On Nov. 5, 2009, 13 U.S. soldiers were killed and many more injured. The evidence will clearly show that I am the shooter.¡±

Hasan, a 42-year-old American-born Muslim who is representing himself, was in a small courtroom just a few kilometers from Fort Hood¡¯s Soldier Readiness Processing Center, where he said he opened fire four years ago on fellow soldiers preparing to deploy to Afghanistan.