It's been reported in the daily fail that the man (who remains) arrested was known to authorities and had mental health issues.
There's more taboo about mental health in African cultures, its seen as mystical and woo, so more likely you are outcast or hidden by family, more likely you'd not consent to share info with family. So there's an absence of protective factors of mental health.
Psychotic delusions often take on themes of the era - persecution by government or agencies, thinking news is speaking directly to you, suicidal nihilism being examples.
But lots of people with psychotic delusions don't inflict violence on others.
My own opinion is that there'd need to be some kind of personality disorder as well, that's probably untreatable, that you're unlikely to be rehabilitated, and you'd need lifeline supervision.
But how do you prevent this from happening in the first place? There is work going on around health inequalities but community groups and leaders need to come forward and take ownership as well I think. Maybe a government enquiry. Mental health services can't continue like this.