Lance Cpl. Liam Tasker was shot on March 1 while he was on patrol with his Springer Spaniel Theo in Afghanistan's Helmand province.
Theo died of a seizure just a short time later.
Colleagues described the pair as inseparable.
Tasker's mother says she thinks the sadness of losing his master may have killed Theo.
"My honest opinion of this is when Liam went down, Theo didn't have the comfort from Liam to calm him down. I truly believe when Theo went back on the kennel that that would have a big, big impact because Liam wasn't there to comfort him and calm him," Ian Tasker, Liam's father, said.
"I don't know why I'm not a vet, I can't answer that question. I'm not a vet. But I would like to believe he died of a broken heart because of Liam," Jane Duffy, Liam's mother, said.
Three weeks ago, the British Ministry of Defense was praised for finding 14 hidden bombs and weapons caches in just five months.
(Copyright 2011 by The Associated Press. All Rights Reserved.)