Like many of the episodes, you are really sad because you can see what lead the killer to do what they did. And its really hard to be fully mad at them.
In this case Josh killed a innocent guy who really seemed to be down to earth, had plans, very nice . etc. But as the story goes on Josh had such a horrific life before hand. Multiple parents, a mother incapable of showing love/being a mother, a third dad who sexually molested him for years. The mother again didn't really seem to care.
And when you hear Josh speak, unlike many of the other killers, you can see the remorse and the pain in him. Both for what his past and what he did. It's ashame Tommy's (man who was killed) brother is almost violently mad towards Josh if he were to meet him in the future. There is no doubt you have every right to be mad. But everyone has a past, sometimes a past that you had no choice in. Tommy's brother needs to forgive because even though it may not seem fair, the hate you hold towards someone will destroy you over time and you will never be happy.
Josh had a tragic life and sadly took a life because of it. This is just sad all around.