WHY DO PEOPLE BULLY? If you are going to be honest about one

I knew on few occasions it's seemed like me & Holly were bullying. But the teacher gave Holly one chance to tell the truth and she said she didn't do the books on purpose. He believes her story. That the bags were beside eahother and books started spilling out on top of eachother & she started throwing random books in!
&& also we know reiltin has said we were bullying too by laughing.& honesly,you and I both know I laugh at anything. But we didn't mean to make anyone feel bad.
I actually am gonna try stop laughing.
I guess people got the wrong end of the stick & I guess we don't realise how we;re making people feel.
So again We're Sorry.
I guess we could spent some time apart now so nothing else goes wrong because I dont want to hurt anyone or start any trouble.

Thanks for being a great friend.

Ps.
Feel Better Soon.
I guess we werent made to be friends aha!

Often because the bully has learnt this behaviour elsewhere - from being bullied their self by either a peer, sibling, parent etc. They feel powerless around the person bullying them, so they bully someone else to feel stronger and more powerful.
Or they're just naturally a complete doüche canoe with no regard to other people's feelings.

This is me were talking about haha!
It's kind of a mishap that people took the wrong way haha.<3

People buly others for many different reasons. Usually, the bully has been rejected in some way, or have other problems and they like to "pass it on" to others. The bully bully's other in order to feel better about themselves and forget their own problems. The bully wants to feel like their on top and that they have no problems. If you want some more information, here's a helpful link :
http://www.bullyingstatistics.org/content/why-do-people-bully.html
There's tons of explanations about bullying on this website above.

thanks