They've got him on an ATM camera at a bank where he withdrew a large sum of money and then is seen making an exchange with two guys; they're looking for the two guys. They think he might have mixed the heroine with a pain medication used for cancer patients that makes the heroine ten times stronger. They're calling it an accident. I wonder why they call these kind of cases accidents instead of suicide, they're killing themselves after all. Another thing, if he had lived, would he be going to jail like the two who sold him the drugs, or would he be going to rehab while they go to jail?
The reason the police had gone to his apartment was because he had failed to pick up his kids.