i am so lost

I am mommy to three little boys aged 3,6,9 and I love them with all my heart. however I am scared of what is to become of my boys my youngest is fine however my oldest has been diagnosed with several disorders which we do all we can to help him with but nothing is working and it is steadily getting worse. I am to the point that I do not know what to do to help him or even save him from himself. my 6 year old is just the opposite he is almost completely emotionless he does not have the correct responses to every day things in life he is very smart and tests at genius levels however does not mind inflicting pain on other children including his baby brother and no matter what i try he just wont stop. i have always tried my best with my boys and am doing everything i can to help them they are under counceling and are in special classes at school to help them but nothing i do seems to be working just today my oldest threatened to stab (  was even acting it out in the air) a lil girl in his class with a pair of scissors. my six year old busted another child in the head with a rock and sent him to the hospital it did not bother him at even when he knew he was in trouble i am totally lost and have tried everything i can think of and feel as though i am seriously failing them as parent my husband is doing all he can as well.