<p>CAMP VIPER, IRAQ -- Lance Cpl. Roland Castellanos was manning a machine gun atop a 7-ton truck when an Iraqi ambush hit his Marine convoy Friday night.</p>
<p>He couldn't see the attackers, only tracer rounds. Swiveling his weapon, he fired 100 rounds into the darkness. In the cab below, the driver also was firing and lost control. The truck rolled, throwing out Castellanos.</p>