Kids threatening other with pencil

One of my son's classmates missed school today because he had intent on hurting another classmate.  It seems he's been talking about stabbing another student with a pencil and he missed school because of it.  Hard to get the whole story from my son on the situation.  He said he and another student talked to this kid the other day to calm him down, but I guess it had not worked.  My son said a student told a teacher about the threat this kid made and that could be why he was out.  Of course with the privacy law you can't get any information on it. 

This is scary cause in elementary school a student in my son's class did stab another with a pencil.  This was in 4th grade (couple yrs ago).  Not only do you need to worry about kids bringing in weapons, but using ordinary items as a weapon.  It's scary because what if this 6th grader gets a hold of a gun and brings it in instead of threatening another with a pencil.  Also what if this kids decides one day that my son is a target cause he looked at him wrong?  Now I got to worry about this. 

Not sure what elementary school this kid came from but it was not the same as my son's old school.  My son said that this kid got kicked out of school before because he did stab another with a pencil.  Not sure if this kid bragged about it, is lying to make himself look big and bad, or if it's true.  My son said this is his friend though and the kid does not bully him in any way.  One worried parent here.