Blackfive has the scoop on the real Sheehan story:

Casey Sheehan’s Sergeant asked for volunteers. Sheehan had just returned from Mass. After Sheehan volunteered once, the Sergeant asked Sheehan again if he wanted to go on the mission. According to many reports (and according to his own mother), Casey responded, “Where my Chief goes, I go.”

Go read the whole thing. Bring tissue.