I'm not surprised at all. Like I said a few posts above, people freak out for all kinds of reasons. It's a real shame they had to shoot him, since it'd be kind of helpful to know what caused him to go off his nut. By all accounts he was a pretty sane guy, and acting quite normal beforehand.
Reminds me of a recent incident with a body-builder and pornstar. He went increasingly loony until his GF called the paramedics saying she was concerned he was suicidal. He was reasonably calm until they got him into the meat-wagon and put him in restraints. At that point he had a panic attack and ripped the handcuffs off of the gurney. Johnny's natural inclination was to tazer him repeatedly until he had a heart attack and died. In his case it was a Michael Jackson level of insomnia that caused him to freak. I wonder if something similar wasn't going on with this guy. Stress and anxiety lead to loss of sleep, which leads to delusional behavior, which leads to death by cop.