1.Why do they bully people? Because they like to see their classmate sad and depressed or so they can get rid of them so they can kill themselves  

http://eschooltoday.com/bullying/Why-do-people-bully.html

2.What causes them to bully people? What causes them to bully is that maybe the family of the person who bully's doesn't love him or take care of he/she. that can cause the bully to feel bad and wants others to feel the same way.        

 http://www.bullyingstatistics.org/content/why-do-people-bully.html

3.Why do people cyber-bully? To make people feel bad so they can kill themselves or because they gone through things and want others to feel the same way as them. they can also just do it for fun but what they don't know is that the person your talking bad things about has feelings and they don't show it.

https://ieonline.microsoft.com/#ieslice

4.Why do they always bully the (weakest) people? Because its an easy target and they won't do anything back to hurt the bully

http://www.sciencechatforum.com/viewtopic.php?f=47&t=23211

5.Why does bully happen a lot? Because the bully thinks he/she has more power than the person they are hurting like they can:

• Tease
• Talking about hurting someone
• Spreading rumors,
• Leaving kids out on purpose,
•  Attacking someone by hitting them or yelling at them 

http://www.stopbullying.gov/kids/facts/