I understand your mum to be worried but really your brother, statistically, is in much graver danger just driving around than getting murdered in the UK.
Where is he in the UK?
How old is he?

Personally when I travel I dont go to areas I dont know when it is dark......

I was buying a kebab once up Seven Sisters road in London and it kicked off big time... I locked myself in the car but couldn't pull away...got the taillights broken. Learnt my lesson... just dont go to such areas so late. Shame this boy didn't get a second chance

I hope your can help your mum get some perspective.