drj- stressful I cannot offer any advice on what the vials contain. I guess you know your options. Ask bro about it, call the police or ignore it. Tread carefully and stay safe. If it is addiction- behaviour can not bely the true emotional content of the addicted. The only person who can answer these questions is your bro. You can offer support- but he has to do the work. Be careful not to fall into the emotional guilt thing.
Support to you, empathy for your bro.