Recalls Winfield, "The sergeant came back to me and said, 'You know, it's a terrible situation, but from our end, it's a he-said, she said conversation. And there's nothing we can do about it.
"I was floored," said Winfield.
Sen. Nelson's office told ABC News they had no record of a call from the Winfields.
Meanwhile, in Afghanistan, Staff Sgt. Gibbs was becoming suspicious of Winfield, according to other soldiers.
An Army investigator asked Cpl. Morlock during his taped confession if he thought Gibbs was serious about maybe having to "take out" Winfield.
"Oh, f___ yeah, for sure, definitely," answered Morlock.
"So you didn't take that as a joke," said the investigator, "or like maybe it was just bull____."
"[Gibbs] doesn't bulls____," said Morlock. "He doesn't need to."
Chris Winfield told ABC News he gave his son a message from the Army. " I told him, this is what they told us to do, you know, duck. Keep your head down. Stay away from this guy. Do the best you can. You know? And it's tough. As a parent, you know? I didn't expect him to come home."
Adam Winfield did come home, but he is now charged with pre-meditated murder. Three months after trying to blow the whistle, he says Sergeant Gibbs forced him to take part in another murder.
He claims he aimed his rifle over the body of the Afghan victim.
Said Emma Winfield, "It's heartbreaking. You know, again, I'm so thankful that he made it out of there alive. But he doesn't deserve to be treated the way he's been treated. When in February, he reached out. And as parents we did what we could do. And we will probably always regret that we didn't do more."
"But we were working from the place that he was afraid for his life," said Emma. "And we weren't going to do anything to risk his life. And now, in essence, we're just fighting for his life. And fighting for justice to be done."
At Fort Lewis Monday, the military held its first hearing on the case, as lawyers for Corporal Morlock sought to have the videotaped confession kept out of evidence, maintaining he only played along during the murders, and that he was heavily medicated with prescription drugs during the interview.
"My client did not kill anyone," said Waddington. "He did not use any bullets or grenades to kill any of those individuals."
Waddington said his client had little choice but to go along with Gibbs. "If your sergeant says, 'Let's go to this village, we're going to sweep this village and he throws a grenade at someone, and threatens you that if you're not on his team and you're a possible snitch and you're going to get beaten or killed by him, then you're going to role play along with it."
A lawyer for Sergeant Gibbs declined to comment on the case, but it is clear the other soldiers will seek to blame him for forcing them to participate. Eric Montalvo, the lawyer for Adam Winfield, told ABC News that he believes Gibbs is "essentially a serial killer," calling him "Mansonesque."
The military says the investigation of the murders also led to the discovery of widespread drug use at Forward Operating Base Ramrod.
Corporal Emmitt Quintal, one of the men charged, blamed the drug use on "Bad days, stressful days, days that we just needed to escape" in a taped interview with Army investigators.
Asked how frequently the men used drugs to escape, Quintal responded, "I'd say probably anywhere from three to four, every three to four days."