Even if you believe the shrink crap, your link describes a person who snaps and kills people at random. This would not seem to fit the bill if the official narrative is true. He killed his mother, than traveled out of his way to deliberately murder a kindergarten class. It was not randomly killing people he came across.
No, in cases of Amok they don’t just start killing randomly, even though they do kill indiscriminately once their rampage starts. There is usually some definable trigger event, and after that, they still do some type of planning for their spree, even if that simply involves obtaining a weapon.