What was ironic about Kamal's death in The Kite Runner?

Kamal's life took an ironic turn for the worse in
The Kite Runner after his participation in the attack on Hassan
following the kite-flying tournament. Though a somewhat unwilling participant, Kamal was
one of the boys who held down Hassan while Assef victimized him. During Baba and Amir's
escape from Kabul, they discovered that Kamal and his father were hiding in the same
tanker truck. Kamal was virtually unrecognizable: Withered and catatonic, he had no
recognition of the scene unfolding around him. Amir overheard only part of the story.
Kamal had apparently been attacked by four men (possibly Russian soldiers) and was
beaten and victimized--just as Hassan had been. After the tanker truck had finally
reached Pakistan, it was discovered that Kamal was dead: He had died from inhaling the
fumes inside the tank. Out of grief, Kamal's father siezed a gun and shot himself in the
head.