Hi there, strangely, I was talking to my mum last night about exactly the same thing. I was asking 'what if I flip and my mind takes over'?
She told me that a lot of murders committed by who you would imagine as 'decent' people are motivated by jealousy/ money and that unprovoked attacks are usually carried out by 'yobs' and to be honest, I feel a lot better now knowing this because I don't consider myself greedy and certainly don't see myself as a yob so I tell myself it's impossible

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Whenever you get thoughts like this, whatever you do is that you must not read into them. Whatever you are doing at the time (eg. washing dishes), change to something different, something that's going to make you feel happy or make you laugh. Concentrate attentively on you are focusing on. It's all I can think of doing to be honest. Hope this helps!
Oh, and do not watch the news, I warn you lol. I'm coping a bit better now that I don't watch it or read about it.