Kyle Shanahan apologized, and he did so in a much calmer tone than he showed Sunday in his debut as the 49ers coach.

What he apologized for was screaming at a sideline official who didn’t hear him yell — three times — for a timeout in the third quarter of the 49ers’ 23-3 loss to the Carolina Panthers.

Instead, officials saw the play clock expire, issued a delay-of-game penalty on fourth-and-1 from the Panthers’ 21-yard line and prompted Shanahan to change course, opting not to go for it offensively and instead settle for a 44-yard field goal.

Video and photos of Shanahan screaming quickly made their way onto the web.

It was Shanahan’s first true temper tantrum as 49ers coach, not that it shocked him.

“No, I didn’t surprise myself. I’ve made that mistake before,” Shanahan said Monday. “And if (the side judge) was here, I would apologize to him now.

“He’s trying to do his best just like I am. I was just frustrated,” Shanahan said. “I wanted a timeout and I yelled it as loud as I could three times and he just didn’t hear me. I was mad at him for it. It’s not his fault. He’s focused on the game, too. Hope he has no hard feelings towards it.”

And Shanahan hopes the league doesn’t fine him like it did in 2012, when he got levied $25,000 for pursuing replacement officials off the field as Washington’s offensive coordinator.

“I’ve been fined before. You can Google it,” Shanahan said. “I’ve learned the hard way, so I try not to (argue).

“But, I’ve got a lot of respect for those guys. They take their job as seriously as I take mine and we treat it all almost life-and-death. Sometimes I’m not going to always have the best reactions when I’m upset about something, but it’s definitely not personal.”