Kaleta was assessed a major penalty and game misconduct for the hit, which happened
during the third period.
Here is a video explanation from the NHL:
NHL Director of Player Safety Brendan Shanahan says Kaleta was in full control and had ample opportunity to avoid contact with Richards. Despite the fact Richards returned and completed the game, Richards was hit from behind dangerously close to the boards, according to Shanahan.
Kaleta is a repeat offender, being suspended two other times during his playing career.