I'm curious what they were heard saying, when the government agent said he heard the men "talking about the shooting." If it was "aw man, I missed, rats!" then lock him up and lose the key. If it was "I tried to get him to notice me so I wouldn't die in this @@$#&#^!! flood" then convict him of... Being In A Flood While Stupid? I don't have a lot of blame for people trying to survive.
You're right, trying to attract attention for rescue is another possible explanation. Guess my assumptions have turned negative since watching looting of non-lifesustaining material.