Creepy Tenant?

I’ve lived in my apartment for 2-1/2 years by myself. I’ve never experienced something like this. They must be new. I live in a closed apartment complex and there’s 4 floors. My side of the apartments has the 4th floor whereas across the way there’s just 3 floors. All of the apartment entrances face inside towards a small courtyard. I have a doorbell camera that notifies me of motions. I’ve noticed the past 3 nights there’s been this man walking around and sometimes even standing in front of my unit and just looking out into the courtyard or at the sky. I didn’t think much of it the first night. Then the second night I came home from work at 730 PM and he was standing there again in front of my unit and looking out down at the courtyard again. I didn’t acknowledge him and quickly got into my apartment. The third night, tonight. I walked out of my apartment to get my guy friend downstairs. As I was walking I noticed the man across the way at the 3rd floor unit stairway across my floor. I recognized him because he was wearing the same overalls as yesterday. I’m not sure why he was lingering there. I was thinking maybe if he’s new he’s just taking a walk to get to know the area? When my friend and I were walking back to my apartment you can see him try to hide in the stairway and peak out to look at us. Then of course my doorbell camera catches my motion as I’m entering the apartment. When I close it the camera continues to record this person peak out and come from the stairway. At least he saw my guy friend with me so I’m hoping it would scare him off. Then when my friend was leaving the guy was now on my same floor but still down by the other units. My friend just stared at him as he was walking to leave. This behavior is just so creepy ! I want to email the landlord but not sure if I’m just being crazy ?? How would I even address this. I just want to know if this guy is actually a tenant too or not. I also want my concern to be confidential..