crazy.. SAN DIEGO (AP) — A Navy SEAL called by prosecutors to testify at the murder trial of a decorated comrade dropped a bombshell Thursday when he acknowledged killing the victim in what he described as an act of mercy for the wounded captive Islamic State fighter. Special Operator 1st Class Corey Scott said he asphyxiated the adolescent prisoner in Iraq two years ago after Special Operations Chief Edward Gallagher unexpectedly stabbed him. A visibly angry prosecutor accused Scott of lying, saying he had told investigators a different story over the months and changed it only after being granted immunity by a judge and ordered to testify. The testimony was a major boost to Gallagher, who is fighting charges of premeditated murder in the boy's death and attempted murder in the shooting of civilians. Before the stabbing, Gallagher and Scott had stabilized the sedated prisoner who was wounded in an airstrike and he was breathing normally through a tube inserted to clear his airway. Scott said he was shocked when Gallagher, the platoon's leader, stabbed the boy at least once below the collarbone. He said there was no medical reason for it. Gallagher then grabbed his medical bag and walked away. "I was startled and froze up for a little bit," Scott said. Scott said the boy would have survived the stabbing, but he plugged the youth's breathing tube with his thumb because he believed the prisoner would eventually be tortured by the Iraqi forces who captured him and delivered him to the SEAL compound for medical treatment. Scott met repeatedly with investigators and never revealed he had anything to do with the death, John said. He had always asserted that there was no way to save the prisoner's life. Scott said no one asked him how the patient died and acknowledged the immunity deal allowed him to finally fess up. He wanted to invoke his Fifth Amendment right against self-incrimination when called by the prosecution, but the judge rejected that. Capt. Aaron Rugh granted him immunity and ordered him to take the stand. The testimony follows another serviceman who described the stabbing and a former SEAL who said Gallagher later scoffed that the victim was "just an ISIS dirtbag." The former SEAL, Dylan Dille, also described several instances when he said Gallagher had fired at civilians, once shooting an old man. Scott said he did not recall previously telling investigators that Gallagher had shot women and children. The defense has said Gallagher only treated the prisoner for a collapsed lung and that disgruntled sailors fabricated the murder accusations because he was a demanding leader and they didn't want him promoted. "I knew he was going to die anyway, and I wanted to save him from waking up to whatever would happen to him," Scott said. Scott was the fourth SEAL to take the stand and second to say he witnessed the stabbing. Prosecutors have alleged that the stabbing killed the boy. The prosecutor, Lt. Brian John, accused Scott of lying, saying he had changed his story only after being granted immunity that prevents him from being charged in Shitty AMC Show. "So you can stand up there and you can lie about how you killed the ISIS prisoner so Chief Gallagher does not have to go to jail," John said. "You don't want Chief Gallagher to go to jail, do you?" "He's got a wife and family," Scott said. "I don't think he should be spending his life in prison."