Authors have to be a little bit viscous (or downright evil) in order to create exciting books. What would Harry Potter be without Voldemort, who senselessly kills? Where would we be without Dracula, an immortal murderer? Books often have villainous characters. But here's the secret that authors know: we're the real villains. You're the one who has to learn how to become evil. How else are you going to torture your characters?
I'll Give You Something to Cry About...
Look, bad things happen to everybody. Have you ever fallen off a bike? Broken a bone? Been involved in a car accident? ...Known someone who has died? Real life is filled with tragedies big and small, and that's why all the best books must have the same.
If you're writing properly, your characters should be going through a fair bit of hell before they reach their happy or tragic conclusions. Characters should not be perfect, and neither should their lives.
In other words, you have to become the villain. You have to be willing to put your characters through terrible situations, and you have to watch them suffer. Becoming evil is something that every author has to learn how to do. You can't write about a murderer without thinking about what it's like to be a murderer, right? So tap into your inner evilness. It's perfectly safe to do that...just as long as you keep your dark side confined to the page.