If you wish to consider two or three people to constitute a large crowd, that's your prerogative.
I consider it inappropriate to refer to killings committed by individuals or small groups as "mob violence."
what is your threshold, numberwise, that defines a small group as different than a mob?
The dictionary definition in the particular case of black- on-white violence is woefully inadequate and very outdated.
We are way past ‘propriety’ here.