Carolyn Kaster/AP
The tombstone of US Army Capt. Humayun S. M. Khan is seen in Section 60 at Arlington National Cemetery in Arlington, Va., Monday, Aug. 1, 2016.
Khan, a Muslim-American Army captain, was killed in a suicide car bombing in Iraq in 2004.
"He was an amazing leader. He was an amazing man," Sgt. Laci Walker, who worked with Khan, said in an interview on CNN. "If you worked for Capt. Khan then you knew you were taken care of. You knew that everything was going to be OK."
Meanwhile, retired US Army Maj. Gen. Dana J.H. Pittard - Khan's commander in Iraq - wrote in a Washington Post editorial that Khan was "a wonderful person" and "a great officer."
"Our country needs more men and women like Humayun Khan and the countless others who willingly and humbly served this great nation of ours without reservation or recognition," Pittard wrote.
Thomson Reuters Khizr Khan challenges Republican presidential nominee Donald Trump to read his copy of the U.S. Constitution at the Democratic National Convention in Philadelphia, Pennsylvania
Trump has repeatedly criticized Khan's parents since the two gained national prominence at last week's Democratic National Convention, where they denounced Trump's candidacy and questioned his knowledge of the US Constitution. A recent poll suggests the unexpected feud has done significant damage to Trump's campaign.
"I join all those who stand in support of the Khan family," Pittard wrote in the editorial.
"This family is our family, and any attack on this wonderful American Gold Star family is an attack on all patriotic and loyal Americans who have sacrificed to make our country great. Any politically or racially motivated attack on the Khans is despicable and un-American."
Watch the video of Sgt. Walker's interview below: