He is the leader of the marines on the field and the second in command during the mission to LV-426 against the Xenomorphs. He is a good sergeant and his men like him. He treats Ripley with respect, apreciates her efforts to help and doesn´t like Hudson very much because of his stupid comments.
When the Sulaco reached LV-426, Apone readied his men for the drop in typically boisterous fashion before taking his place on board the unit's APC for the drop to the planet's surface. After breaking up Hudson's attempts to embarrass Ripley, Apone led his men into the colony complex.
When they find the colonists, he leads his man to the place only to find them hung on alls and dead. He also watches one of the alien come from one of them that was still alive. He kills the alien with a flamethrower and causes the aliens to wake up and attack them.
He is taken prisoner by the Xenomorphs for breading and it is implied he is later killed because of it.