Three former U.S. soldiers dispute the official investigative report that blames human error for a friendly fire accident that killed six others, including two Green Berets, on a secret mission in Afghanistan. In the soldiers' first interviews, they tell Bill Whitaker that a technical limitation of the aircraft sent to their aid was mostly to blame for the war's deadliest friendly fire incident. They warn more could die if the aircraft's targeting system isn't changed. Whitaker's report, a three-year investigation in which 60 MINUTES obtained the classified report of the accident, will be broadcast on 60 MINUTES Sunday, Nov. 12 (7:00-8:00PM, ET/PT) on the CBS Television Network.

In June 2014, five Americans and an Afghan soldier died when an Air Force B-1 bomber dropped two 500-lb. bombs on them during a nighttime firefight. U.S. soldiers wore infrared strobe lights on their helmets to distinguish them from the enemy fighters. Air crews that fly low in support operations can see the soldiers' strobes through night-vision goggles from the cockpit. On this particular mission, an Air Force B-1 was sent to the aid of the soldiers under attack by Taliban fighters. But the bomber was unable to see the soldiers' strobes.

"We thought it could," says Derrick Anderson, a decorated former Green Beret captain and veteran of more than 80 combat patrols in Afghanistan. The classified report obtained by 60 MINUTES blames Anderson, commander of a 10-man "A-Team" for misidentifying his team-mates as the enemy when he called for the airstrike. It says, in part, "Though this was a challenging set of circumstances, had the team executed standard tactics, techniques and procedures, and communicated effectively, this incident was avoidable." Anderson responded, "I disagree with that statement."

Killed by the bombs were Green Beret Staff Sergeants Scott Studenmund and Jason McDonald, Private First Class Aaron Toppen, Specialist Justin Helton, Corporal Justin Clouse and Afghan National Army Sergeant Gulbuddin Sakhi. "My gut dropped. I just felt something sink to the bottom of my stomach, and I was like, 'No…This isn't happening,'" recalls Anderson, whose career with the Green Berets was effectively ended by the report's criticism of his actions. He has left the Special Forces.

The classified report also said the fatal airstrike was driven by a "false sense of urgency." But former Army National Guard medic Staff Sergeant Brandon Branch, who gave first aid to a victim, disagrees. "They can call it that, but they weren't there."

Henry Montalbano, the Green Beret team's former communications sergeant, says the report doesn't fully address the "root cause of the friendly fire incident…There's an aircraft carrying out close air support missions that can't detect the common marking mechanism at night-time. It's dangerous to use an aircraft that's incapable of picking up infra-red strobes," he tells Whitaker. Montalbano has since left the Green Berets.

Whitaker also interviewed Occidental College professor Woody Studenmund, the Gold Star parent of Green Beret Staff Sgt. Scott Studenmund, who was killed in the bombing. Studenmund also criticizes the use of the B-1 bomber, saying, "When we send our soldiers into battle, it's wrong to have them using a weapons system which isn't capable of doing what it's supposed to be doing. It isn't murder, but it's close."

More than three years after the incident, the soldiers interviewed by 60 MINUTES fear a similar mistake will happen again. Says Anderson, "We still have U.S. service members throughout the world in harm's way that are going to rely on this aircraft again. And that's what disheartens me. That's what scares me. That's what I'm mad about."

Anderson tells Whitaker he and his men did nothing to cause the deaths of their fellow soldiers. "At the end of the day there's nothing myself or my team sergeant did that day or failed to do that day that caused the incident to happen…We made the decisions that we thought were best at the time on the ground for the guys that were being shot at."