It was a non-contact injury to his right knee. He was skating and just dropped to the ice, unable to put any weight on the affected leg as he immediately left for the dressing room.
The only update given since is that he'll be reevaluated after the all-star break with a lower body injury.
I've tried to rationalize and console myself with thought processes along the lines of, "He didn't tear his acl because there would be no use waiting two weeks and then reevaluating," but the reality is we have no idea if he'll be out two weeks or never play again, such is the nature of hockey injuries.