It was when Boston's Pastrnak barely fifteen minutes into the second period, in the third quarterfinal against Carolina, put 3-1 that the accident occurred.
The home fans thumped so hard in the plexiglass behind one of the penalty booths that a large disc came loose - and fell over the timer Joe Foley.
Foley was taken out on a stretcher and taken to hospital.
He is reported to have been alert after the incident but his exact condition is unclear.
Boston won 4-2 in front of the home crowd after Taylor Hall scored the team's last goal.
The victory means that Boston reduces the match series against Carolina to 2-1.
Watch the clip of the accident in the player above.