The incident took place during Wednesday's Blackhawks-Ducks game in Anaheim, Seabrook caught Anaheim's Corey Perry with a hit near the end boards that knocked Perry down.
Seconds later, Wisniewski laid a crushing hit on Seabrook that knocked the Chicago defenceman out of the game. Starting from the faceoff circle, Wisniewski sped at Seabrook and launched himself off the ice and into the defenceman at the end boards.
Wisniewski was assessed a minor charging penalty on the play, while Seabrook appeared dazed on his feet before collapsing to the ice.
"Mr. Wisniewski delivered a retaliatory hit to the head of an opponent who never had possession of the puck," explained NHL senior vice president of hockey operations Colin Campbell in a statement.
"There are certain hits in the game that are tolerable if you got the puck," stated Blackhawks coach Joel Quenneville after Wednesday's game. "But if you hit a guy without the puck, you could kill a guy. It's the most dangerous hit in the history of the game. He tried to hurt him. If that's not intent, that's as bad a hit as you can ever have in the game."
Wisniewski, a former member of the Blackhawks, showed remorse for his actions but didn't agree with the eight-game penalty.
"I am truly sorry that my friend Brent Seabrook was hurt on the play," said Wisniewski in a statement. "I certainly wish him the best. I am, however, very disappointed in the length of the suspension. Eight games is incredibly hard to swallow, especially in comparison to other recent hits that have resulted in lesser punishment."
The suspension was not the first for Wisniewski this season. He served two games for a hit on Shane Doan of the Phoenix Coyotes in early November. He was also suspended for one game (crosscheck) in March of 2008.