Cops are on their way

I didn't write about this yesterday, I didn't think it would matter since it really has nothing to do with us...but now it's starting to involve us. It happened again, another break-in at the place next door. This time two windows were victim (my boss just had them replaced) and they stole even more phones. The shop owner is starting to say she wants to pull the store out of there, go somewhere else.
Well, this morning I came in about 8:55, turned the copier and computers on and settled into my chair for some e-mail checking. I see this guy looking into our windows and I think nothing of it, people do that all the time. He comes in and asks me what our office is for. I tell him it's real estate, did he need help with anything? He's a young guy, quiet. He's freaking me out, he's looking around the place.
"Are you the only one in here?" he asked.
Why would you ask me that? "No," I lied. "My boss is in the back taking the garbage out."
He's looking around the office. At our windows. At my desk. Into the back.
"So you're not alone?"
I shake my head. I'm freaking out, I wish we had like a push button under the desk like banks have to activate some sort of alarm. Why can't someone call right now?
He looks around some more and asks me what time the library opens.
"I have no idea, they have a different schedule every day."
He walks out, heading toward the library.
I call my boss right away and tell him what happened. He tells me to call the cops, that he would be here in a few minutes. Not surprisingly, my boss makes it here before the cops do. I apologize to my boss maybe I'm overreacting but he says it's better to be safe than sorry, what with the break-ins next door. We can't be too careful.
My boss is outside with the cops right now. He just came in to tell me they (the cops and my boss) saw the guy sitting outside the library and they just asked him what was up. He said he was just curious. They told him not to come into my office again. He said fine. The cops ran a check on him and he came up clean, only a domestic under his belt. He lives in the local shelter. I feel like I might have overreacted, I don't want the guy to think that I just go around calling the cops on people. But he freaked me out. He gave me goosebumps. Bad vibe.
Now I will feel like an asshole if something happens to our office after we have left, because not only do we have people watching this block for the phone place next door (and God knows if they are watching our place, we have quite a few computers and my boss doesn't have cheap taste), but now I've gone and pissed off some guy who could retaliate just because I called the cops.
*SIGH*