SAN DIEGO – Mike Tomlin and Le’Veon Bell knew exactly what had to happen.

With five seconds left, the Pittsburgh Steelers down by three points and the ball inside the 1, Bell had to get into the end zone.

It was a wildcat way to win, which the Steelers did 24-20, stunning the San Diego Chargers and sending tens of thousands of Terrible Towel-waving Pittsburgh fans into delirium at Qualcomm Stadium.

Bell took the direct snap, ran left and was slowed in traffic before diving for the end zone and getting the ball across the line as Donald Butler dragged him down.

“It was time to go to the mattresses, if you will,” said Tomlin, the Steelers’ coach.

“We had to do what was required to win. Le’Veon gave us an opportunity to win, and we were trying to do everything we could to move the football.”

Bell said it was the most meaningful touchdown of his three-year career. “The game-winner on the last play of the game, that’s what you dream about,” he said.

“I got to get it in,” Bell said. “We still had a timeout left. I was thinking we still have a timeout left, so I’m thinking, ‘OK, maybe if I get stopped, maybe run like 4 seconds off and get a timeout and we could kick a field goal.’ I wanted to end the game right there.”

Bell ran 21 times for 111 yards.

San Diego rookie Josh Lambo kicked a go-ahead, 54-yard field goal with 2:56 left.

Here are some things that stood out as the Steelers moved to 3-2 and the Chargers fell to 2-3:

HEINZ FIELD WEST: It’s never been hard for fans of visiting teams to get tickets at Qualcomm Stadium, and Steelers fans practically overran the aging concrete bowl, which could be hosting its final year of the NFL because Chargers owner Dean Spanos wants to move to the Los Angeles area.

“First I’d like to thank Steeler Nation,” Tomlin said. “How about the support that we had in the building tonight? We get that type of support just about all of the time we’re on the road, but it doesn’t get old. We appreciate it.”

OPPOSING VIEW: Chargers quarterback Philip Rivers didn’t appreciate the many fans clad in black and gold.

“It was a tough environment tonight. It was like being on the road,” Rivers said.