Dylan had some stubble the day he died as well as long hair. He may have been not shaving so often as a general rule? Eric was just clean-shaven and his hair a buzz-cut in all his media appearance.
The dirty nails in the end may just be from material preparations of bombs, powder handling, gas, etc. He may not have thought: ''Better be clean than sorry, will do my manicure before I die tomorrow.''
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"Is evil something you are? Or is it something you do? My pain is constant and sharp and I do not hope for a better world for anyone. In fact, I want my pain to be inflicted on others. I want no one to escape."
- American Psycho - Bret Easton Ellis (1991)