What is this bajrang dal and how serious is it?

So today morning I was at a park which I go to atleast thrice a week, just to spend some quiet time alone and do my own thing like reading a book or completing work. On most days, I see a lot of couples coming there but today there was not a single one to be seen. And as I sat there I saw a gang of young men with lathis enter the park, roam all over and leave in 10 mins. I asked the guard what's the scene and he said they are bajrang dal people and since it's valentine's day, they roam around to ensure there are no couples doing unholy things in public spaces. I was like, what??