This is a frightening situation and you have to take threats like these seriously.  Any act of violence or threat thereof is absolutely impermissable.  If he made this threat elsewhere the consequences would be severe and they should be at home as well.  We are sorry you are having to experience this.  It must be very painful for you to have to hear such things.  

The good news is that there is help out there.  It is great that he is currently in counseling.  You probably already have, but make sure his counselor is aware of the threats he has made.  The counselor needs to know so that he can address them with your son and further assess the situation.  If he makes these threats again and you feel he may act on them, call the authorities.  It may sound extreme, but it's too serious of a threat not to do.  If your son has demonstrated violent behavior in the past towards other people or animals, this is another dangerous sign it may be best to get him into a residential treatment facility.  

With situations like these, it is best to find a professional to dialogue with as every child and every home environment is going to have a different plan to maintain safety.  Call a family support agency in your area or call us.  We are a hotline that is specifically for parents and teens and with the dangerousness of this situation, we would love to speak with you about how to proceed.  We have a long referral list of agencies from all over the country and are good at safety planning these sorts of incidents.  Please call.

Counselor, Dominic
Boys Town National Hotline
1-800-448-3000
www.parenting.org