Once the clock hit zero in Kansas City after the Chiefs' 21-13 win over the Raiders on Thursday, it appears that the drama wasn't quite over at Arrowhead Stadium.

When the two coaches headed to midfield to shake hands, we didn't exactly get a handshake. Instead, Chiefs coach Andy Reid gave Raiders coach Jack Del Rio a tap on the shoulder, and Del Rio clearly hates being tapped on the shoulder because look at that death stare that he gives Reid.

Reid & Del Rio postgame pic.twitter.com/LSu6W6L7nY — Vikings Blogger (@firstandskol) December 9, 2016

Let's freeze frame that so that you can see it clearly.

Jack Del Rio gives Andy Reid a cold postgame stare. NBC/NFL

After Reid tapped Del Rio, plenty of people on Twitter were surprised by Del Rio's death stare.

If there's bad blood between the two, it might be due to some comments Del Rio made in October after Oakland lost to Kansas City 26-10.

Following that game, Del Rio called Alex Smith and Chiefs' offense "gimmicky."

"If [Smith] got to rely on throwing the ball, it's really not his strong suit, but if you allow them to run the ball, do some of their gimmicky things, then he comes to life," Del Rio said. "That's what they were able to do today."

As for Thursday's game, Del Rio and Reid did eventually shake hands, but it doesn't look like Del Rio is too happy about it.