The former Manchester United striker struck his opponent in the head after Petrasso appeared to back into the Swede and tread on his foot.

After the intervention of the video assistant referee (VAR), on-field official Ismail Elfath booked Petrasso and showed a straight red to Ibrahimovic for violent conduct.

Going down to 10 men in the 41st minute did not stop Galaxy from recording their first win in five attempts.

Kamara was the man to supply the decisive intervention, collecting Emrah Klimenta's flicked header and racing towards goal before beating two defenders and Impact keeper Evan Bush with a confident low finish in the 75th minute.

The victory leaves Galaxy seventh in the Western Conference, while Montreal, winless in three, are second bottom in the Eastern Conference.