The release of Army Sgt. Bowe Bergdahl in a prisoner exchange with the Taliban has sparked questions about the circumstances related to the sudden disappearance and subsequent search for the soldier.

Amid the questions, the family of a soldier from the same battalion Bergdahl served with -- who was subsequently killed in action -- hopes a thorough investigation of those circumstances will be conducted.

Cheryl Brandes is the mother of Pfc. Matthew M. Martinek, 20, of DeKalb, Ill. Martinek was stationed at Fort Richardson with the 1st Battalion, 501st Parachute Infantry Regiment, 4th Brigade Combat Team (Airborne), 25st Infantry Division. She believes Martinek was killed in action while he and fellow soldiers searched for Bergdahl, also a member of the 501st.

Martinek deployed to Afghanistan's Paktika Province during the first quarter of 2009. He and Bergdahl served there until Bergdahl disappeared in June 2009.

After the 28-year-old sergeant’s disappearance, Department of Defense reports say Martinek was critically injured on Sept. 4, 2009, when his vehicle was attacked with an improvised-explosive device followed by a rocket-propelled grenade and small arms fire.

“What we hope will not be lost on the American people is the true heroism of the soldiers who risked their safety to relentlessly attempt to rescue Bowe,” Brandes said of her son’s death.  “One of those brave men was our son and brother Matthew Martinek.”

Martinek was flown to Landstuhl Regional Medical Center in Germany for treatment, but a week later he died from the injuries he sustained in Afghanistan.

Reached for comment Monday, U.S. Army spokeswoman Lt. Col. Alayne Conway could neither confirm whether Martinek or other members of his regiment were actively searching for Bergdahl when they were attacked, nor speak to whether Bergdahl had deserted his post in the first place.

CNN reports that other U.S. officials are saying little about the events that left Bergdahl in Taliban hands for nearly half a decade. According to CNN, when asked about the issue Sunday, Defense Secretary Chuck Hagel avoided the question.

"Our first priority is assuring his well-being and his health and getting him reunited with his family," Hagel said. "Other circumstances that may develop and questions, those will be dealt with later."

On Monday, Pentagon spokesman Adm. John Kirby said U.S. officials "still don't have a complete picture of what caused (Bergdahl) to leave his base that night."

"But let's not forget, he was held captive as a prisoner for five years. Five years by himself," Kirby said. "That's a pretty high price to pay for whatever impelled him to walk off that base."

While Conway and other U.S. officials could not confirm Martinek's mission at the time of his death, the families of those injured and killed that day -- as well as the other soldiers who were present -- are certain Martinek and his regiment was searching for Bergdahl.

“We only ask for a thorough investigation and an honest accounting of the facts,” Brandes said. “The one thing we are certain of is that whatever happened, Matthew would still have gone out to rescue Bowe.”

The soldiers Martinek served with at the time reflect a sentiment similar to Brandes’s. Pfc. Ryan McNeely, a former infantryman with the 501st at the time, who has since been medically discharged, served with Martinek and was there the day he and the rest of their patrol were ambushed.

“We set up a rotation schedule throughout the night for people,” McNeely said. “The next thing I remember is getting woken up by a buddy of mine and a grenade going off near my head.”

McNeely says he's confident Bergdahl deserted his post, and he believes Bergdahl owes his fellow soldiers an explanation for what happened that day in June 2009. And if Bergdahl did in fact desert, McNeely believes his time spent as a prisoner of war isn’t justice for the lives lost searching for him.

“I know people are saying his time over there is payment enough, but I don’t quite think it is,” McNeely said. “It might be enough payment for the actual desertion, but what his desertion did actually cost a lot of lives. I think he should be held accountable for that.”

Brandes, like any mother, sympathizes with the Bergdahl family and can only imagine the joy they must be feeling to have their son home, out of harm’s way.

“Despite the controversy surrounding (Bergdahl’s) returning home, a family’s love should never be underestimated,” Brandes wrote. “Please keep our fallen and their families close to (your) heart.”

Channel 2's Shannon Riddle contributed information to this story.