Melvin Ingram did not let up, driving his helmet into Drew Brees' chin right after he released a pass in the third quarter.
Seconds later, the San Diego Chargers' celebration of Demorrio William's interception return for a touchdown turned into disappointment when Ingram was flagged for roughing the passer.
Then everything fell apart for the Chargers in a flash.
The Saints moved 68 yards in five plays for a touchdown. The Chargers went three-and-out. Then the Saints drove 90 yards in nine plays for another score.
Just like that, a potential 31-14 lead had turned into a 28-24 deficit, and San Diego (3-2) never recovered in a 31-24 loss to previously winless New Orleans on Sunday night.
"Obviously it was a critical play," Chargers coach Norv Turner said of Ingram's penalty. "You can't make those kinds of errors, and we will learn from them."
In addition to the loss, the Chargers saw Drew Brees — a quarterback they drafted in 2001 and let go in 2006 — break Hall of Fame quarterback Johnny Unitas' half-century-old record by throwing a touchdown pass in his 48th straight game.
"I guess you really couldn't have written a better script for tonight," Brees said. "To break the record, to get the win, and the fashion in which we won — really a complete team effort all the way around.
"The amazing thing about a record like this is it spans over the course of four seasons and hopefully we can keep it going for a while," Brees said. "There are so many people that are a part of this."
Brees' 40-yard pass to Devery Henderson eclipsed the mark of 47 consecutive games with a touchdown pass Unitas set from 1956-60.
Brees finished with four touchdown passes, including three to Marques Colston, giving the seventh-year receiver a franchise-record 52 TD catches with the Saints (1-4).
At Brees' request, the NFL allowed head coach Sean Payton, assistant head coach Joe Vitt and general manager Mickey Loomis — all serving various suspensions in connection with the NFL's bounty investigation — to attend the game. They and Unitas' son, Joe, saw Brees pass for 370 yards, enough to put him over 30,000 yards in his 100th game as a Saint.
Afterward, Brees took an elevator near the Saints' locker room up to the Superdome's suite level to share a few moments with Payton, Loomis and Vitt.
"It gave us a good mojo for sure," Brees said of Payton's presence. "I love my coach, so glad he could be here. Mickey and Joe Vitt as well. It is special for our team, special they could be a part of this record."
NFL Commissioner Roger Goodell, the one who suspended Saints personnel in the bounty matter but also granted Brees' request for Payton, Vitt and Loomis to attend the game, chimed in on his Twitter page shortly after the record fell, writing, "Congrats to (at)drewbrees & his teammates on breaking Unitas' record. Amazing accomplishment by great QB & leader. We're proud of you, Drew."
Philip Rivers passed for 354 yards and two touchdowns to former Saint Robert Meachem, but had two costly turnovers in the final quarter.
"I can't tell you how tough it is to lose a game like this," Rivers said. "We were right there. We were up by 10 points and just didn't get it done. We have a great team, a championship caliber team. But we have to win close games like this."
The first late turnover was Roman Harper's interception and 41-yard return on a pass tipped by fellow safety Malcolm Jenkins. That set up the Saints' final score on Garrett Hartley's field goal. San Diego still had a chance to tie in the final minute until defensive end Martez Wilson stripped Rivers and recovered the fumble to seal the victory.
The Saints' defense, which entered the game ranked last in the league, had a hand in the victory not only with the turnovers but five sacks.
"You really have to credit our defense getting pressure on the quarterback," Interim head coach Aaron Kromer said. "That's what made a difference in the game."
After his record-setting completion, Brees trotted to the end zone to hug Henderson. The rest of New Orleans' offense pursued and swarmed around Brees in celebration. Brees took the game ball to the sideline where he continued to accept congratulations. The scoring pass capped an 80-yard drive in which Brees completed all three of his third-down passes, including the touchdown.
Still, San Diego regained momentum, taking a 17-14 lead on Meachem's 44-yard touchdown catch in the final minute of the half.
San Diego went ahead 24-14 on Ryan Mathews' 13-yard run around left end, capping a three-play drive that started after Henderson tipped a pass that Brees threw behind him, allowing Quentin Jammer to intercept it and give San Diego the ball on the New Orleans 25.
Notes: Meachem did not have a TD this season before playing in the stadium he called home for his first five seasons. ... Chargers PK Nick Novak, who was filling in for the injured Nate Kaeding, made a 20-yard field goal but missed a 55-yard attempt in the second quarter. ... Saints TE Jimmy Graham hurt his right ankle in the first half. He returned to the game but was not a factor. ... Saints LB Curtis Lofton had a game-high 10 tackles including a sack.