Here is the record of what actually happened.
1 Samuel 31:1-7 Now the Philistines fought against Israel; and the men of Israel fled from before the Philistines, and fell slain on Mount Gilboa. Then the Philistines followed hard after Saul and his sons. And the Philistines killed Jonathan, Abinadab, and Malchishua, Saul's sons. The battle became fierce against Saul. The archers hit him, and he was severely wounded by the archers. Then Saul said to his armorbearer, "Draw your sword, and thrust me through with it, lest these uncircumcised men come and thrust me through and abuse me." But his armorbearer would not, for he was greatly afraid. Therefore Saul took a sword and fell on it. And when his armorbearer saw that Saul was dead, he also fell on his sword, and died with him. So Saul, his three sons, his armorbearer, and all his men died together that same day. And when the men of Israel who were on the other side of the valley, and those who were on the other side of the Jordan, saw that the men of Israel had fled and that Saul and his sons were dead, they forsook the cities and fled; and the Philistines came and dwelt in them.
The record says that Saul committed suicide. Even his own armourbearer would not dare to strike "The LORD's Annointed."
The Amalekite was trying to ingratiate himself with David and lied to him. His actions were absolutely dishonourable. If Saul asked his armourbearer to kill him to avoid being slain by the "uncircumcised Philistines", why would he ask an uncircumcised Amalekite to do the job? Clearly this so-called "honourable" young man was nothing more than a lying opportunist. He got what he deserved.
I hope you have found this helpful.