What the charts show is the man's tolerance for the meds was very high, since he had a nanograms per deciliter level well above what would be toxic in a non-medicated body. He had probably been taking too much for too long and had grown irrational. Sadly, he died for a ridiculous reason and his blood levels would definitely explain his depression and irrational behavior.
As an example, a heroin dose that would kill a non-user is needed in a heavy addict to just 'get the monkey to sit down'.