The Sharks and Kings skated through a scoreless opening period. Then Scott Nichol lured Los Angeles star defenseman Drew Doughty off the ice with offsetting roughing penalties, opening the door to three straight goals by San Jose.
The Kings never fully recovered.
Ryane Clowe scored twice, Jason Demers added another goal in the second period and the Sharks won 6-3 on Thursday night to take a 3-1 lead in the first-round series.
"Nichol is the reason why they won," Kings coach Terry Murray said. "Three goals were directly responsible for Nichol's game."
Joe Thornton and Joe Pavelski scored in a 54-second span early in the third and Torrey Mitchell followed with his first goal of the playoffs to extend the Sharks' lead.
"I don't know what it is," Doughty said. "They're scoring easy goals. We're giving them tap-in goals and that's not something we usually do."
The Sharks return to San Jose for Game 5 on Saturday night having swept the Kings on their home ice.
"It's a great opportunity," Clowe said. "You take a 3-1 lead and you're going back to home ice to wrap it up. We should be fired up and we should want to close it out right there."
Los Angeles gave up 12 goals in its two home games.
"That's embarrassing," Jack Johnson said. "We're not going to win a game if they score six goals a game. We're a defensive team and if we're letting in that many goals we're in a lot of trouble."
The Kings had a 5-on-3 for much of the final 3 minutes after Dany Heatley was penalized for tripping and Nichol got a 10-minute misconduct, but they failed to convert. The frustrated Kings got two 10-minute misconducts themselves in the closing seconds.
Murray was incensed by Heatley's tripping of Alec Martinez, saying the move could have caused a broken leg or injured knee.
"That's a gutless move," Murray said. "You don't do that in hockey."
The Kings kept their dressing room closed for more than 10 minutes afterward. Even mascot Bailey had his furry head buried in his paws as he leaned on a piece of equipment in the hallway.
"Terry is not happy with us," Doughty said about his coach's postgame speech. "We're not happy with each other. We got to clean it up."
The teams combined for five goals in the second — two fewer than they scored in the middle period in Game 3, when the Kings blew a four-goal lead to lose 6-5 in their second overtime defeat of the series.
"Last game was a wild one, nobody really expected that one, but tonight was more of our game," Clowe said. "Better start, better 60 minutes and not too many ups and downs. It was a grind it down game, the game we needed to play."
Antti Niemi made 35 saves while back in goal for the Sharks after being pulled for giving up four consecutive goals to the Kings before their collapse Tuesday.
"The thing about him, he's determined to come back with a real good one," Sharks coach Todd McLellan said. "I thought he was exceptional. In the second half of the game, he made some tremendous saves."
Jonathan Quick was solid in the first period for Los Angeles, but soon fell apart in losing his second straight. He stopped 21 shots.
"We just weren't good enough," he said. "We let the game get away from us early in the third. That definitely wasn't us in the last two games. We got a lot to prove to ourselves and the fans."
The Sharks stunned Quick with two quick goals to open the third. Thornton was waiting in front of the net and scored on Patrick Marleau's pass at 2:28, then blew kisses to the crowd in celebration of his first goal of the series.
San Jose went up 5-2 on Pavelski's slap shot from the blue line at 3:22 that made it 5-2. The Sharks scored their sixth goal when Mitchell got a rebound with 8:18 to go.
Los Angeles cut it to 6-3 when Alexei Ponikarovsky's shot from the left point found the top of the net with 6:49 left.
"Whatever happened in the third with giveaways, turnovers and lost faceoffs, that's sometimes hard to explain," Murray said.
The Kings haven't won a playoff series since beating Detroit in the 2001 Western Conference quarterfinals. They are 1-9 in series when they fall behind 3-1.
This time, San Jose built a 3-0 lead in the second only to have the Kings close to 3-2 by the end of the period, when they outshot the Sharks 17-10.
Clowe and Demers scored 1:14 apart before Clowe added his second goal.
Clowe's first goal capped a 2-on-1 when he scored behind Quick's back at 3:58. Demers made it 2-0 when he beat a fully sprawled Quick on the left side at 5:12. Both goals came with the teams skating 4-on-4 with Nichol and Doughty off for roughing.
"You just don't want to lose your top defenseman to a player of that stature," Murray said.
With Matt Greene serving a double-minor for high-sticking, Clowe scored on the power play at 9:28. Quick swiped his left hand at the puck too late and the Sharks led 3-0.
The Kings rallied with two goals later in the second. Ryan Smyth's slap shot sailed wide right and Brad Richardson came around the net to push the puck in with 9 minutes left.
Justin Williams then scored off a deflection 3:56 left.
NOTES: The family of Bryan Stow, the San Francisco Giants fan who was severely beaten after the Dodgers' season opener last month, attended the game as guests of both teams. The Sharks paid for the family's tickets and the Kings bought their dinner. ... Smyth has a point in all four games of the series. ... San Jose's Logan Couture, Kyle Wellwood and Ian White each had two assists. ... The announced crowd of 18,234 was the second straight standing-room only sellout. ... The Kings' Murray is one away from his 50th career playoff victory.
(This version CORRECTS name of Sharks coach to Todd McLellan.)