People who clog subway toilets and run away

I witnessed it firsthand earlier.
I was walking toward the sinks after urinating when a tall, well-dressed man in his 20s came out of the stall next to me and headed toward the sinks.
For a moment, I could see the closed toilet lid behind him.
Usually, you hear the sound of flushing before someone comes out, but since he just walked out, I thought it was a bit strange, but I figured someone who looks that neat couldn't possibly be doing something like that.
He calmly washed his hands and left the restroom, but at that exact moment, someone entered holding a child's hand and went into that same stall.
As I was washing my hands and coming out, I heard someone behind me saying, "Hey, don't look, don't look," and then they came out with the child and went to a stall far away..