It was 2-0 before the half-hour mark, as Hernan Bernardello was penalised for bringing down Oscar Boniek Garcia inside the area, allowing the Honduran midfielder to score from the spot.
Nelson Rivas received his marching orders in the 69th minute after picking up a second yellow card for an apparent elbow on Bruin, meaning the visitors had to play over 20 minutes with a man down.
Things got worse two minutes later, as Bruin grabbed his second goal of the game to effectively end the match.
The night ended in complete disarray for the Canadian team, who ended the match with eight men after Marco di Vaio and Andres Romero saw red for a scuffle that started when the Argentine forward kicked out at Corey Ashe.
The first leg of Dynamo's semi-final with the Red Bulls takes place on Sunday, with the return fixture on Wednesday.
Meanwhile, Sporting Kansas City and New England Revolution will contest the Eastern Conference's other playoff clash.