There is no crime here. A call to the police might result only ina CAD entry or an informational report of a couple of lines, but no real investigation. There can be any number of reasons to explain his behavior, and none clearly criminal.
I used to suffer from a period of pretty heavy psychosis related to some PTSD I was experiencing. It’s not uncommon for people struggling with major mental illnesses to completely lack social/situational awareness and not understand that their behavior is suspect or out of line. There were a few cases where I was trying to be kind or make friends with people, and I wasn’t able to read the social cues that my behavior was perceived as stalkerish/harassing and not just friendly or playful. Sometimes it’s just best to let that person know it makes them uncomfortable, so they can recognize it themselves and maybe even correct the situation towards others as well.