It is normal to feel sad when we see bad things go on around us. There are some people that it may come upon that we least expected it to happen to. That is just how unpredictable life can be. Life doesn't come with fair treatment.
There may come certain situations whereby we see bad things happen to good people and at the same time see good things happen to those who are bad, which on a normal sense feels like it is out of place. But the fact still remains that God is just. He is aware of everything that is going on and knows the best.
God is not a God of partiality, for those who sometimes think that way. The Bible tells us that He is a respecter of no man. For every single act we carry out while living on earth—either good or bad—God has a reward that is waiting for each and everyone of us. He wouldn't see the good deeds of someone and overlook them. Neither would He see the bad deeds of someone else and overlook it.
The thing with evil is that it doesn't last. At the end of the day, what is most certain is that good will surely prevail over evil. This has been proven countless times over and over again. When our full trust is on God whatever situations we are faced with we know that it's for the best because God is in control.