5 year old homicidal tendencies

My nephew is only 5 years old, about to be 6, and he talks a lot about death, but his psychologist says that he doesn't understand what death is. He has developed a bad attitude problem, like thinks he can talk to anybody how he wants because his great grandfather and grandma will come stop his mom from disciplining him. Now he knows he can run and tell one of them to get out of trouble. Today, while he and his brother were taking a bath, he tried to drown his brother and when his mom got him out of the bathtub and started to discipline him for this action he told her that he doesn't want a brother anymore. He wants to be an only child. He is very smart for his age he understands more than an average 5 year old. So with this information, can anybody tell me what his problem could be? Why is he trying to kill his little brother?

[jdtm]

If what you are saying is correct, your nephew's parents need to see a medical mental health specialist as soon as possible.  The family doctor should be able to give them a referral to a medical mental health specialist as a child psychiatrist or child neurologist.  I would not wait until a disaster occurs ....