The friendly fire incident that killed five American soldiers and one Afghan soldier in June was caused by failures from the "key members" of the ground team who called in an airstrike from a B-1B Lancer, according to an accident investigation report released Thursday.

A team of U.S. and Afghan soldiers on June 9 were providing security for the Afghan runoff elections in the area of Arghandab when one of the teams came under attack. During the attack, key leaders, including a joint terminal attack controller and the ground force commander, mixed up friendly and enemy locations and incorrectly believed that the bomber's targeting system could identify friendly locations.

"The key members executing the close air support mission collectively failed to effectively execute the fundamentals, which resulted in poor situational awareness and improper target identification" U.S. Central Command investigating officer Air Force Maj. Gen. Jeffrey Harrigan wrote in the report. "While this complex combat situation presented a challenging set of circumstances, had the team understood their system's capabilities, executed standard tactics, techniques and procedures and communicated effectively, this tragic incident was avoidable."

Killed in the airstrike were: Staff Sgt. Jason McDonald, Staff Sgt. Scott Studenmund, Spc. Justin Helton, Cpl. Justin Clouse, Pvt. Aaron Toppen and Afghan National Army Sgt. Gulbuddin Ghulam Sakhi.

The mission

The team of coalition forces began their operation on June 8 in the Gaza Valley of Zabul Province. They were tasked with disrupting insurgent activity and improving security for local polling stations for the runoff elections.

Afghan security forces led the effort, with support from U.S. special operations forces and other coalition elements, according to the investigation.

When dawn broke on June 9, the Afghan troops began searching for enemy equipment and forces in the area. Coalition troops began to see signs that insurgents were following coalition movements. Later that day, the team was attacked with small arms fire, called "pop shots." The teams returned fire, and the enemy stopped the pop shots.

When the operation ended, the coalition troops moved toward three pre-planned locations to wait to be exfiltrated. They broke into three teams, each made up of Afghan security forces, U.S. special operators and other coalition troops at the separate locations. The joint terminal attack controller and the ground force commander were together at the first location, the report states. The Air Force JTAC had served multiple combat deployments, and had supported Special Forces missions before, according to the report.

At 7:15 p.m. local time, the B-1B Lancer arrived on location from al-Udeid Air Base, Qatar, and set up a five-mile orbit around the position. Seven minutes later, the JTAC passed along the friendly locations, including the position of the ill-fated team at position B. Friendly forces were within 100 meters of these three locations, the JTAC said.

At 7:47 p.m., position B took fire. The team radioed the JTAC, telling him that muzzle flashes were pointing out to the west. The JTAC confirmed, and told the ground force commander that the team was taking "effective fire."

The team returned fire. Six of them climbed to a higher ground to maneuver on the insurgents. At 7:54 p.m., the crew on the bomber radioed the JTAC, saying they saw muzzle flashes about 200 meters from a friendly position, "approximately 230 degrees for 150 meters."

The JTAC told the bomber crew that friendlies were marked with strobes, and that locations without strobes were enemy positions. The JTAC asked the aircrew if they saw any friendly marking devices at the ridgeline.

"Negative IR strobes," the crew replied.

All on the ground, and on the bomber, assumed the aircraft's Sniper pod could detect the friendly markers. It couldn't.

Standby for the 9-line brief — the authorization to strike, the JTAC responded.

The airstrike

While this was happening, one leader at the first friendly position was told that a group from position B splintered off.

"This movement of friendly forces was not effectively communicated to the JTAC or Ground Force Commander, which led to the team incorrectly identifying the muzzle flashes on the ridgeline as enemy activity — and incorrect target identification that was accepted by the aircrew," the report states.

The commander believed the team at position B was still taking enemy fire from the location on the ridgeline, which was actually the friendly team.

"The target location was identified by the team based solely on a negative report from the aircrew — the report that the aircrew did not see friendly marking devices at that location," the report states.

The JTAC had passed along to the aircrew that the target position was 150 meters from position B. When he passed along the authorization, however, he said the closest coalition forces were 300 meters away. The aircrew didn't question the change in location.

Twenty-one minutes later, two bombs from the B-1 landed on the ridgeline. The team of six was still at the position, and none of them survived the strike.

'Our hill'

After the strike, the rest of the team from position B grew concerned. They radioed first, saying the bombs hit "our hill." They made their way up to the hill, arriving 7 minutes after impact.

When they arrived, they found Studenmund still alive, calling out to them "help me, I can't breathe." A medic attempted to treat him, but was unable to because of the extent of his injuries, the report states.

Members of the task force and a quick reaction force searched the strike location to recover remains and equipment. The teams searched for nearly three hours and up to 75 meters from the site of impact. The remains of five of the troops were recovered, with the sixth recovered the next day.

There was a ramp ceremony at Kandahar Airfield, and then the remains were flown back to Dover Air Force Base, Del., on June 12.

Sniper pod

The Air Force's B-1s are outfitted with the Sniper pod, which was the result of an urgent need request in 2006 for advanced targeting in close air support missions. The pod gives the B-1 the ability to identify targets without other aircraft or ground personnel, and provides a full 360-degree view. In addition to the B-1, it is in use on the F-15E, multiple variants of the F-16 and the A-10, according to the Air Force.

For the B-1, the pod provides high-definition views for weapons systems officers. The pod, however, cannot pick up infrared strobes, which the crews in this mishap relied upon to located friendly forces. The night vision goggles used by the pilots could only pick up the strobes at limited ranges, of up to 7,000 meters.

Killed in the strike

The Americans killed in the strike were all Army, and served in different units across the country.

Clouse, 22, of Sprague, Washington, was assigned to 2nd Battalion, 12th Infantry Reginment, 4th Infantry Brigade Combat Team, 4th Infantry Division out of Fort Carson, Colorado. It was his second tour in Afghanistan after enlisting following high school graduation in 2010. He was from Sprague, Washington. He is survived by his mother, father and brother.

Toppen, 19, of Mokena, Illinois, was also a member of 2nd Battalion, 12th Infantry Regiment, 4th IBCT, 4th ID. He enlisted in 2013, and this was his first deployment. He is survived by his mother and two sisters.

Helton, 25, of Beaver, Ohio, was a member of 18th Ordnance Company, 192nd Ordnance Battalion, 52nd Ordnance Group, out of Fort Bragg, North Carolina. He enlisted in the Army in 2010 and was engaged to be married. He is surived by his mother, father, two brothers and one sister.

Studenmund, 24, of Pasadena, California, was a member of 1st Battalion, 5th Special Forces Group, out of Fort Campbell, Kentucky. He enlisted in the Army in 2009. This was his first deployment. He is survived by his mother and father.

McDonald, 28, of Butler, Georgia, was also a member of 1st Battalion Special Forces Group. He joined the Army in 2004 and served one previous deployment to Afghanistan and two to Iraq. He is survived by his wife and two daughters.