Friend's child a big problem?

I will try to keep this as clean cut as possible. These children are like my own, I love them dearly and so does my best friend, their mother. Her and her husband have tried everything and I have done my own research (their schedule is incredibly busy) and am worried.

The older child (lets call him bruce) does okay. He used to be just as bad with his behavior but he has grown out of it, from what I gather. He still lies and does what he wants from time to time but for the most part seems to be pretty normal. I do believe he does manipulate the adults more than meets the eye, however I also understand that every child does this to a certain degree. The bigger problem here is the Bruce's younger brother (we'll call him Wayne).

Wayne is five. He is not a bad child that I see. But it is like he has a compulsion to continue bad behavior, like it is an itch he cannot scratch. He urinates himself at night, especially after a bad day where he has gotten into trouble. Lately, the problem has escalated to defecation in his pants during the day. At school, he refuses to do his work and though I understand he is only five, he outright refuses to behave for any reason it seems. He is very smart and remembers almost everything. But now he is committing vandalism too. He went to the bathroom at school and drew on the wall with markers, and does the same at home no matter what punishment is given, no matter what is taken away, no matter what chore is assigned. He steals things often as well, from food to toys to things that belong to adults, such as cell phones and iPods. He sneaks out of his room at night to do these things. He has a hard time sleeping, or going to sleep. He is also fascinated by fire, I have caught him with lighters several times, as have his parents. He throws tantrums very often, although they do not last long anymore because we told him that fake tears do nothing. The first time he heard this he immediately just stopped and looked at us with no problems. These tantrums used to last anywhere from fifteen minutes to an hour or so depending. He lies without any hesitation as well, even when we know the truth, caught him in the act, he will still look at you and lie. But he is also sweet, or at least he acts like it a lot of the time. One other thing that has caught my attention is some of the things he has said, like "I am going to chop your head off." to his brother, and he seems to also be fascinated by death. We had an incident where my cat died and he talked about it non stop for a while, mentioning it every couple of days. The thing is the roughest movie he has EVER watched was Get Smart. Seriously, these kids are disney maniacs and watch hardly anything else. So it can't be movies or tv, they do not own cable. He also smiles during punishments, like time outs and what not. I hope I am wrong here but I have told my friend, who agrees, that he needs a psych evaluation at the very least. Is it possible he is a sociopath? Though I understand that only a doctor can make this claim I would like opinions and any other help I can get. I am very worried about him as are my friends.