CEDARBURG, Wis. -- The parents of a Cedarburg soldier killed in Iraq have filed a Freedom of Information request for military documents about their son's death.

Stephen and Kay Castner said that they are hoping to find evidence backing their claim that Humvees are unsafe for use in Iraqi convoys.

Their son, Stephen Castner, 27, died in July when the Humvee he was riding in was hit by a roadside bomb.

Castner's father raised questions about training and equipment given to his son's unit even before the soldier's death.

The Castners are asking the Army for detailed records of guerrilla land mine attacks on Humvees operated by Castner's unit. They also want records of operations to detect and remove guerrilla mines in advance of convoys.

The Castners want training records from Camp Shelby in Mississippi and the detailed reports on the attack that led to their son's death.

U.S. Rep. Jim Sensenbrenner is helping expedite the FOI request.