How can I write an essay about why Grendel killed so many people in the Beowulf story?

How can I write an essay about why Grendel killed so many people in the Beowulf story?
I want to know some strong facts that Grendel have to kill so many people.
i have some & are that he was jealous, people were scared of him. but i need more.. can anybody help me? Thanks (:

Although Grendel was probably just a big bad troll in the lost sources of the Beowulf epic, in the epic as we have it he’s a descendant of Cain, a less-the-human creature resulting from generations of inbreeding among murderers and other sinners. He’s alienated from God and from everything bright and good. He has lived down under that murky swamp longer than anyone remembers, and he seems not to have bothered anyone until the sounds of merriment and praising God coming from the newly completed Heorot stir him up. (These are the “hall joys” that other Old English poets wrote about.)

But how many people does he actually kill? He comes to Heorot after everyone is asleep that first night, and the next night he comes back. After that, the members of the court seem to realize that their beautiful new palace is uninhabitable and stop sleeping there. Grendel continues to come back every night and tear the door off its hinges (inference: some man has the job of rehanging it every morning), but there’s never anyone there for him to eat. Then when Beowulf comes and he and his men bed down in the hall, Grendel kills one of Beowulf’s followers, Hondscuh–and that’s the last person he kills, because then he reaches for Beowulf and realizes a second too late that this is someone he definitely doesn’t want to tangle with. It’s his mother who kills Aeschere the next night.

Here’s a thought that you may be able to use: Grendel is what he is in this epic because he’s descended from Cain, the first murderer. But Cain’s crime wasn’t plain, simple murder–it was fratricide. (OK, I know, who else was there for him to kill? But he found someone to marry easily enough.) In the first part of Beowulf, fratricide is the worst thing anyone can do. It’s what has stained Unferth (figuratively) and, it seems, made him unable to kill Grendel. Now, Grendel has human ancestors. Yet he kills humans and eats them. Could cannibalism be seen as just a step beyond fratricide? In any case, he seems to take after the old man.