U.S. Army Maj. Nidal Hasan offered no evidence in a hearing ending Wednesday on whether he\'ll receive a death sentence for the Fort Hood mass shooting. The Army Medical Corps officer who fatally shot 13 people and injured 31 others in the Nov. 5, 2009, shooting -- the largest mass murder at a military installation in U.S. history -- said simply, \"The defense rests\" when it came time to rebut prosecution testimony and offer witnesses or evidence to support an argument he should be spared the death penalty and receive life in prison instead. Hasan is acting as his own attorney and has agreed with prosecutors he walked into the medical deployment center on Fort Hood to kill as many soldiers as he could as part of a jihad to protect Muslims and Taliban leaders from troops heading to Afghanistan. His \"defense rests\" statement Tuesday produced an audible gasp in the courtroom, CNN reported. The judge in the court-martial, Col. Tara Osborn, then recessed the trial, removing jurors from the courtroom until Wednesday. At that time, prosecutors and Hasan will have an opportunity to present closing arguments, after which the military jury will begin its deliberations on his sentence. The jury of 13 senior Army officers found Hasan guilty Friday of carrying out the mass murder. Hasan, who turns 43 Sept. 8, could become the first U.S. soldier in 52 years executed in the military\'s death chamber at Fort Leavenworth, Kan. All jurors must agree on the death penalty, and President Obama must approve it. Otherwise, Hasan could receive life imprisonment. Shortly after the recess, Hasan\'s three standby military attorneys asked Osborn to let them present information he chose not to use -- in particular, a sentencing-expert report that contains potentially mitigating evidence, such as Hasan\'s record of community service. \"If no one is making a case for life, there is only death,\" Lt. Col. Kris Poppe, a standby attorney, told the judge. But Hasan called the counselor \"overzealous\" and said he didn\'t want the report admitted, The Wall Street Journal said. Osborn sided with Hasan after repeatedly asking if he understood his decision. She said Hasan\'s decision was ill-advised, but he had a constitutional right to represent himself. Earlier Tuesday, Hasan asked no questions of prosecution witnesses -- including the spouses and parents of six murder victims -- who testified about their struggles since the shooting. The struggles they spoke about included alcohol abuse, depression, suicidal thoughts and unraveled relationships. \"When a parent loses a child, it creates an irreplaceable void,\" said Jerri Krueger, mother of Sgt. Amy Krueger, who was 29 when Hasan killed her. \"I live with that every day,\" Krueger said. No witness addressed Hasan directly or looked at him at the defense table, CNN said. Hasan himself watched all the witnesses, occasionally wiping his nose, the network said.