Great commute today. It was actually in the 40s.

(After being in the 30s every morning this week.)
Something amusing happened. I had barely started my ride when some guy on a mountain bike came out of the woods onto the road behind me. I was keeping an eye on him in my rear-view. He was sort of hunched over and looking all serious. I just kept going normally and he kept pace behind me.
Approaching a stop sign. As I usually do, I slow down so I can stop if necessary. MTB rider blows by me and through the stop sign.
"Okay", I thought, "I'll play cat & mouse with him." I followed him down a hill and onto the trail. We got to a slight incline and he began to lose speed so I dropped him and put a bunch of distance between us.
Next stop sign coming up. I slow down and I see he's rapidly overtaking. No cars coming, so I hit the pedals and deny him a flyby. Put some distance back between us.
Yet another stop sign. This one I have no peripheral views so I kind of have to slow down substantially before I'm sure it's safe to cross. This gives the guy ample time to overtake, and he does, and blows through that stop too.
I decided to stop playing leap frog and just paced him a few bike lengths back. He got agressive on the pedals a few times but I just hung out behind him. Eventually he turned off on a road. Giving up? Not sure.