1. In a murderous frenzy as if possessed by a demon.
2. Wildly; without self-contro: "He was running amok as he was shooting at everyone."
3. In a frenzy of violence, or on a killing spree; berserk.
4. In or into a confused or disorganized state or condition; out of control, especially when armed and dangerous.
5. In or into a jumbled or confused state or situation: "No matter how many experts we consulted, all of our travel plans went amuck!"
7. Etymology: from Malay amuk, "attacking furiously". Earlier the word was used as a noun or adjective meaning "a frenzied Malay"; originally from a Portuguese form amouco or amuco.

Today anyone who wantonly shoots people is said to have run amuck (run amuck is the usual phrase to use); and so it indicates mental derangement, a madness to do violence or to kill indiscriminately.