For example, PTSD is a mental dysfunction - stimuli that are not threatening are interpreted as threatening by the brain. This could lead to you killing someone, but the act of killing someone isn't what defines the PTSD.
The behavior of killing yourself or someone else may the most beneficial (and therefore "logical") response to a real threat to you or your kin.
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H̓̇̅̉yͤ͏mͬ͂ͧn͑̽̽̌ͪ̑͐͟o̴͊̈́͑̇m͛͌̓ͦ̑aͫ̽ͤ̇n̅̎͐̒ͫ͐c̆ͯͫ̋ ̔̃́eͯ͒rͬͬ̄҉
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