If you want to make a character death sad well here's how it's done.

Death is sad in real life. It always is. But in a book its more complicated because the characters aren't real. If you want the audience to care about a side character's death then you need to do 2 things.

1) Make sure that person has a goal that we can relate to

2) Stop them from getting that goal

The audience does not care about people who do not fight for something. If you want me to care about someone you need to give them  something to achieve, something that means a lot to them. So that when they die it's sadder because that person wanted something and never got it.

You wouldn't care about a character if they didn't have their own goals and didn't do anything for the story. In order for a death to be meaningful he person has to be aiming for something good and miss.

An example: A man tries to rescue his family from drowning but before he can do it he gets stabbed in the back by the villain.

This works because the person was trying to do something good and then they were stopped.

Comment below if you have a better idea of what makes a death tear-jerking.