It appears one of the Huskies' top players was punched by a fan after the game ended.
Video posted on YouTube seems to show UW tight end Austin Seferian-Jenkins taking a fist to the face from a stranger as Cougar fans rushed the field after their improbable victory Friday night.
Seferian-Jenkins has remained tight-lipped about the incident, but took to Twitter to address it, telling a friend publicly: "It's all good." And responding to a direct message request from KOMO News with "I'm fine. Thank you for asking."
A University of Washington spokesman wouldn't comment about what happened on the field, but off the gridiron, fan reaction has been swift.
"At the end of the day it's only a game," said UW junior Nate Iannuccillo. "You don't want to see anyone get hurt like that."
Sophomore Danielle Olson echoed those sentiments.
"We understand that WSU and UW have always had maybe a heated rivalry," Olson said. "But no one expected something like that to occur."
Of course, it's not the first time the Apple Cup has descended into something not so great. In 2010, fans from both sides hurled snowballs at each other, and one band member ended up in stitches.
Eight years prior, it was beer bottles that flew through the air.
Campus police in Pullman are now investigating this most recent incident. WSU's assistant police chief Steve Hansen says they are going under the assumption it was likely a fan who was behind this.
"We're starting an investigation to see if we can track down what happened there. We're trying to get the video from the stadium to see what went on," Hansen said. "I don't know who else it would be other than a fan."
If the person is found, he could face a charge of assault or disorderly conduct.