He was posthumously promoted to master sergeant.
The soldier was found unresponsive on base, according to information from the Army. The cause of his death is under investigation.
Ruiz was on his first deployment to Afghanistan, according to information from 3rd Special Forces Group.
"Today we lost a great soldier, leader, husband and father," said Lt. Col. John Sannes, Ruiz's battalion commander, in an e-mail from Afghanistan. "He was a Ranger-qualified senior noncommissioned officer selected for [promotion to] master sergeant that led by example, always diving in alongside his soldiers to complete any mission or task."
Ruiz enlisted in the Army in 2003 as a cook. He served in the 82nd Airborne Division at Fort Bragg for more than eight years, deploying three times to Iraq.
He was assigned to 3rd Special Forces Group in April as the NCO in charge of the forward dining facility in Afghanistan.
Ruiz also was a volunteer with Tragedy Assistance Program for Survivors, or TAPS.
"We are saddened by the death of our dear friend and dedicated TAPS volunteer Pablo Ruiz" said Bonnie Carroll, TAPS president and founder, in a statement posted on the group's website. "During this Memorial Day week and all the days ahead, our hearts are with his family, friends, and the children of the TAPS Good Grief Camp whose lives he profoundly touched."
In an interview with the TAPS Magazine in 2014, he said, "I would want this to be done for my child if something happened to me."
Ruiz, who lost a close friend in combat in 2007, also volunteered for the TAPS Courage Campaign with both the Washington Wizards and Washington Capitals. Pablo was recently featured in a PenFed Military Salute at both Wizards and Capitals games for his service in uniform and as a volunteer for TAPS.
He leaves behind his wife of nearly 19 years and one daughter, according to TAPS.
Ruiz's awards and decorations include the Meritorious Service Medal (second award), Army Commendation Medal (fifth award), Army Achievement Medal (fifth award), the Iraq Campaign Medal with three campaign stars, Parachutist Badge, Air Assault Badge, Combat Action Badge and Ranger Tab.
Ruiz was posthumously awarded his sixth Army Commendation Medal and his third Meritorious Service Medal.