sorry for your loss, and may he RIP.
however, its hard to say he od-ed on aMT or the other stuff he was taking, so a clear cause of death this isnt. just speculation.
what aMT are you guys into? 200mg? as a normal dose?? thats waaaaaay waaaaaay off, at least in my experience (30 is good enough for me, i cant imagine ever going above 100), though i have heard others needing that much for effects (cant remember the name at the moment)
again, i hope people will be more careful in the future.