According to Kelly and Hannity in disguise guests he was seen making a drug deal, he ran one way and other guy the other way. He also apparently was a very good snitch and well known to cops covering the beat which is known for drug dealing. Very long rap sheet. And apparently a University - I think Maryland U - did drug testing and was positive for heroin and pot.
Also was known for acting up when arrested.
Which leads to my speculation that he ate his stash and had a seizure in the back of the wagon. Flip flopping around like a fish until he banged his head.
The statement re drug testing made reference to the U of Maryland hospital, where he was taken for treatment. The ER probably did a screen. The actual tox test either isn’t back yet (likely), or is being kept secret. The thing is, the post-mortem test isn’t going to be much use. Lots of time for whatever was in his system to clear out, and lots of hospital drugs to be added.