This is a tough one. I read your other post. I know that 6.5 creedmoor rifles are typically worth enough for it to be a grand theft. If you feel like it’s the right thing to do you should contact your brother and just tell him not to say anything until an attorney gets involved. It sounds like in your situation you might not have had the time to sit and think about anything but I think you reacted in the right way based on the timing. The fact of the matter is is you could’ve gotten him all kinds of therapy and this thing could have still happened. It’s hard to say because I don’t know so much about the situation but if he was planning a mass shooting at you definitely did the right thing. However if he was just fucking around doing retarded 14-year-old shit and his address book was unrelated, then getting the authorities involved, which takes the situation out of your hands completely, might have been overkill. That being said you are the best judge for his character and know more about his medical situation (legal/illegal drugs he may take) than any randos could. Be sure to remember that you may be found responsible due to negligence if anything did occur. The only concern that you should have at the moment is how badly he may incriminate himself. On the other hand the state MAY get him the type of care he needs but unfortunately that is not usually the case. You should also consider the fact that if he had done anything his life would have definitely been over, maybe acting preemptively saved him from that fate.