We interrupted it!

My partner and I were making a turn when I spot a car going past us the opposite direction. I noticed it didn't have a registration sticker nor a front license plate. I took a quick glance at the driver who is looking at me pretty hard. Well, I could make a sharp turn and try to catch him, but I really wanted to stop by Starbucks so I let him go. As we pull into the parking lot we see four individuals and two cars on the other end talking and all of them give us hard looks. We stumbled into the middle of things. One of the cars looks like the car I just saw, but how could he have gone the opposite way, turn around and beat me here? However it damn sure looks like the car and the driver. I go in and get my coffee. As I'm conversing with the barista and two of them come in. They circle me and I do not like this at all. So I maneuver where I can see them and cover my gun. The barista is clearly concerned and whispers for me to stick around which I do. They buy a drink and leave. I get mine and get in the car and tell my partner what happens. We notice one of the cars has left. We drive by to get the plate but one of the males is standing there covering it up. This can't be accidental. These guys are definitely up to something and waiting for us to leave. So I pull around the plaza and sit and watch. After a minute he pops the hood. Okay, that's it! We're not waiting around. I start a conversation and find out he is the guy I saw. So now I have probably cause to detain him. He has two traffic warrants that I arrest him for. The other guy is clear. Whatever these guys were planning we interrupted it.