So, the anger is subsiding... and the parental lobe is shifting into second gear and you are full of fear. Fearful you should be because drugs on any level is pulls your child into a danger zone unknown to you prior to this experience.
What kinds of drugs are they using? How long have they been using? Why? Why? Why? How introduced them to drugs, where are they getting them, where are they using them? Your mind is racing as well it should be, think it through. Think about their recent behavior patterns. Have they changed? When did they change? Are they talking about new friends? Are they talking at all?
Drugs and alcohol use in tweens/teens is even more dangerous if they are mixing it up a bit. Please don't be soothed if you find out that marijuana is their drug of choice. I can't stress enough that minimizing the use of marijuana makes the drug even more dangerous. Does that make sense to you? Think about it for a moment. Whenever we as human minimize the risk of anything in life we may possibly find it creeping into our lives and out of control.
Your young one isn't going to get the fear issue. At their young age they feel they are invincable. They will let you know quickly that you are blowing this way out of proportion and this is no big deal. You may hear "this is the first time I ever tried this stuff"... don't buy it folks. It is very unusal for a parent to catch them in the act the very first time. I am not surprised by the reaction I get from parents that their child just started using... I was once in that spot, in denial. I understand it completely. Denial protects us as parents from knowing more than we care to know. But the quicker you get over the denial issue the better off you and your young one will be.
Denial kills. It kills relationships, it kills addicts... it kills our young ones as well. Face your fear and process it... think it through... figure on the worse case scenario. How will you handle it? Think of the best case scenario...is there one? Yes there can be because hopefully you have been alerted to the drug use in its early stages.
It is important that you do not allow yourself to be frozen by fear. Take a deep breathe, think it through. Expect the best outcome but prepare for the worse one. Again, you must own your fear, feel it and put it away. I have never experience a good response from my daughter when I approached the situation being motivated by anger or fear. So while your fears are justified do not let them consume you. Think it through... parents talk it out and prepare for the next phase.
God bless you... look to God and pray for wisdom.