Not because of a bad performance, not because West Brom were on the losing side - but because someone was checking their mobile phone to see what happened in the other Premier League games of the day.
The Baggies, of course, were on the winning side - beating Manchester United 1-0 at Old Trafford.
But Welshman Pulis was nevertheless on edge. Indeed, he told the BBC that he doesn't like playing so late due to the temptation to check other results. And that's exactly why he went 'berserk' at someone, telling them to focus only on all things West Brom.
When Pulis did find out that West Brom's closest rivals had all won, however, he admitted the Manchester United win became all the sweeter.
He explained to reporters: "I don't like playing at this time. I went berserk today because someone had a mobile on trying to find out the other scores. I told them we only focus on us.
"I came in after the game and they told me all the teams below us had won so it makes it even sweeter."
West Brom's Old Trafford victory took them to the magical 40-point mark in 13th place in the Premier League. Now time to build for next season for Pulis and co.
Let's hope he doesn't have to go too berserk in future...