The injury occurred during the final minutes of the first period. Eyssimont checked Jensen into the boards, it was not a perfect hit, which resulted in Jensen taking an awkward fall and hitting the boards head first. Jensen's head and neck took a majority of the impact of falling into the boards. Take a look at the replay, which shows the hit and the fight that was caused as a result of the hit.
It seems that Jensen was knocked out as a result of hitting the boards head first. Medics can be seen rushing onto the ice to assess the situation, Jensen was removed from the ice on a stretcher. Officials decided to end the period early, although they added a minute and thirty-one seconds to the second period so that no time was lost.