Incident on NJCL train #7281 Sunday night?

Train #7281 to Long Branch on Sunday night was about 20 minutes late, apparently due to "police activity". When it did arrive, I noticed that every car seemed to have flat spots on its wheels, so I wondered if it had made an emergency stop.

I was on that train last night. We were held at the Newark Airport station for about 20 - 25 minutes; with no explanation. I didn't see any cops or unusual activvity, although I was seated on the track (not platform) side and could have missed something.