The cause behind the sudden Monday morning passing of U.S. Army Specialist Derek McConnell has not yet been released. The wounded veteran, who lost his legs in the Afghan conflict in 2011, was discovered dead in his bed.

The 23-year-old soldier's mother, Siobhan Fuller-McConnell, told NJ.com that the reason her son died has not been determined.

Funeral arrangements have not been released.

According to her posting on the Facebook page “Team Derek,” McConnell's fiance Krystina Dressler was unable to rouse him from what she thought was sleep early Monday. 

"I tried everything I could think of," Dressler wrote about finding her high school sweetheart. "I held out hope when I listened for a heartbeat as I tried to wake him and there was none, and even still held out hope when they told me he was gone."

McConnell joined the Army in 2009, deployed to Afghanistan in March 2011 and was wounded in July 2011. While patrolling in Kandahar's Zahri District he was hit by two improvised explosive devices, losing both legs and suffering a host of serious injuries including a fractured skull.

For the rest of his life, he endured surgeries and rehabilitation, finally learning to walk on crutches with the use of prosthetic legs.

“He fought hard right until the end," his mother wrote on the Team Derek page. "He will be missed and never forgotten.”

McConnell had three brothers and a sister.

McConnell was honored with a homecoming when he returned from Walter Reed Medical Center in Bethesda, Md., to Parsippany last September. In January 2013, the Army promoted him to the rank of specialist.

At the time of his death, he and Dressler were planning to be married in December; the pair were the top vote-getters in the Operation Tie The Knot contest. 

Contest organizer Peter Stavrianidis, who owns Venus Jewelers, told NJ.com that his store has not decided what to do with the prize and is focused on sending sympathies to the McConnell family.