Probably not random:

A 14-year-old schoolgirl has been seriously injured after a substance, believed to be acidic, was thrown at her and another teenager outside her school in west London, with a staff member also becoming hurt while trying to help them. The girl remains in hospital with potentially life-changing injuries following the incident at Westminster Academy, Westbourne Park, which took place after school hours on Monday afternoon.

The Metropolitan Police says it believes the two teens were approached on Alfred Road by a male “who threw a substance at them before fleeing down Harrow Road”.

I think “potentially life-changing” probably means the acid melted her face.