He may have been scammed, we've all had run ins with door to door metal salesmen, and sometimes they'll try and pass off gold coloured mercury as liquid gold to try and swindle you.

Just this morning, a man tried to palm off some copper so shit it'd make Ea-nasir blush. I said "Look, buddy, I'm in the market for copper because I'm making High Bandwidth Memory chips in my bathroom right now, and you're offering copper not even suitable for roof gutters. Please come back with some actually good copper and then we can talk".

injecting gold would count as erratic behavior as an initial decison

As I recall the comments from his social group implied that he was erratic before and also experimenting with amphetamines, though I'm certain it was the gold