A strange encounter in the mall?

[I dont but]

So I was in the mall today, in the shoe store, and I see a large man with a full black beard in a thick black trench coat. He had on those 80s big square thick glasses, and he looked around in his early 50s. He was intensely staring at this blonde girl, and making odd facial expressions. A couple minutes later his trench coat came undone and he was masturbating under it but didn't seem to notice until people started hurriedly leaving the store. Then he casually covered up and walked out, and I was just standing there still trying to understand what was going on. What would you have done?