5 yr old depression or worse-help!!

Hi,

My son is in kindergarten and in the beginning of December we suffered the loss of our dog in which
I had for 14 years and my son grew up with this dog.  Recently he was at school and said he wanted
to kill himself and when confronted about it by the teacher he understood that it meant you die forever.  When I asked why he said this he said Mommy when you get older then you will die and I will miss you and I don't want that to happen. I obviously soothed him of that thought and have since got the book Lifetimes that deals with death.

Today I got a call from school that my son was being mean to his friends and threw something that hit one of his friends.  He was sent to the office and they called me to see if I could speak with him because he was being mean and because he was crying uncontrollably.  I spoke with him to try to get him to relax-he said he didn't want to go to school because they make him do school work, I miss you mommy, I want to go home.  I calmed him down and spoke with the office at school and asked them to just watch him-possibly he was tired and acting out but they said they would monitor  his behaviour.  He has been having some difficulty listening, following directions, being disruptive etc... but I have never had a phone call before.

We also had parent teacher conference yesterday where they were concerned that my son seems to have the hand shakes when he concentrates on doing things,etc...should I be concerned?

Any and all help would be greatly appreciated.