what does it mean if a stranger takes pictures of you?

so I was at mall today & I was eating at the good court & I noticed this guy was looking at me like A LOT. so I just ignored him & then I glanced at him to see if he was still staring at me & he had his iphone up & pointed directly at me & he was pressing the screen like 5 times then he looked at me & when he saw I was looking at him he smiled & then left. idk what he was doing but I hope he isn't a phsycopath. what does that mean?