Former Impact defender Laurent Ciman could not have anticipated a better return to Montreal.

Ciman scored in his first game back at Saputo Stadium since being traded in the off-season as expansion-side Los Angeles FC overcame an Ignacio Piatti hat trick to defeat the 10-man Impact 5-3 on Saturday afternoon.

Ciman's goal, a blistering free kick from 30 yards out, put LAFC on the board in the first half. The veteran defender, who refused to hide his frustration after being let go by the Impact in December, blew kisses to the fans after scoring against his old club.

A large portion of the 20,302 in attendance gave Ciman a standing ovation.

"Today's a perfect day for me," said Ciman. "The fans cheered for me before the game, during the game, after the game. They cheered when I scored. Montreal will always have a place in my heart.

"That goal was for my wife and kids. That's the first thing that came to mind."

The 32-year-old, who spent three seasons with the Impact, beat Montreal goalkeeper Evan Bush with a hard driven shot that found the top corner of the net in the 24th minute.

"Shots like that either end up in the goal or the stands," said Ciman, who cut Montreal's lead to 2-1.

Ciman's goal was just one of many in a game that had a bit of everything: a first-half hat trick, an own goal, a red card and three penalty kicks.

In the end, Los Angeles (4-2-0) came from 3-1 down at halftime to score four unanswered goals against an Impact side whose defending looked shoddy even before going down a man.

Montreal's Victor Cabrera was shown a straight red card for a tackle on Marco Urena in the penalty box in the 31st minute. Bush made the save on Urena's ensuing spot kick, one of his career-high 14 saves in MLS.

Carlos Vela made up for Urena's miss in the 83rd minute. With the game tied 3-3, Vela fired a shot down the middle from the spot, the game-winner, after Daniel Lovitz took down Diego Rossi in the box.

Substitute Latif Blessing scored an insurance goal in the 89th for LAFC, which have won two straight games.

"Two penalties today, a red card, it's comical," said Bush. "And these guys (the referees), you can't even have a conversation with them to ask them what they saw. There's a bit of arrogance there that needs to be cleaned up. Because if you don't know what you did wrong, you can't correct it.

"If the calls are good or not, that's beside the point for me. It's the matter of how they conduct themselves."

Things were looking good early on for Remi Garde's men, who have now lost three straight.

Montreal (2-5-0) jumped to its first two-goal lead of the season within 16 minutes of the opening whistle.

Piatti scored his first of the game in the ninth, firing home a rebound into the roof of the net from in close.

He scored again seven minutes later, from the penalty spot. Piatti's fantastic footwork helped him evade tackles before goalie Tyler Miller took him down in the box.

Down to 10 men, Piatti made it 3-1 just before halftime as he let a perfectly weighted lob from Jukka Raitala bounce twice before firing his shot past Miller. It was Piatti's first hat trick in Major League Soccer and first career hat trick since 2013, when he played for San Lorenzo in Argentina.

But the second half was all Los Angeles.

A missed clearance in the 18-yard box fell right to Benny Feilhaber, who scored his second of the season in the 52nd minute.

The visitors tied the game five minutes later when Raitala tried to flick the ball away from danger, only to send it into his own net.

"I'm disappointed we were leading 3-1 at halftime, even down a man, and concede four goals in the second half," said Garde. "We're making way too many mistakes. We need to be more determined to protect our goal. We conceded five goals, but we could have given up even more."

It was the first all-time meeting between the Impact and LAFC.