Citizens don’t fully appreciate how much knowledge, courage and self-control law enforcement officers regularly display in highly stressful circumstances.

But that is no reason to excuse an overzealous Charleston County deputy sheriff who last week, after a car chase, punched a man who was in his car with his hands raised and in the cross hairs of a North Charleston police officer’s gun.

And Deputy Cory Shelton did himself no favors when he said afterward, “All I know is I was finally primary on a pursuit. That’s all I care about.”

The chase, the punch and the remarks were all caught on video.

Indeed, Deputy Shelton remarked after the suspect’s capture, “That’s going to be a good video.”

No, it wasn’t.

Officials aren’t ready to pass judgment on Mr. Shelton’s actions, which are being reviewed. Maj. Jim Brady said that “possibly” Mr. Shelton could have used a more measured approach. Possibly?

Geoff Alpert, a criminal justice professor at the University of South Carolina, however, said it is not a good idea for an officer to rush up to a suspect, who might be armed. He could get himself shot.

Mr. Alpert also said that some police agencies require a secondary pursuer to make the arrest after a chase because the lead pursuer’s adrenaline is likely to be racing.

That sounds like a reasonable practice for all police agencies.

But it also raises a question about police chases themselves — when they are justified and how far and fast they should go.

Last August, Charleston County Sheriff Al Cannon was arrested on an assault and battery charge after he slapped a suspect who had led him on a high-speed chase due to a traffic violation. The U.S. Justice Department decided not to pursue the charges. And Mr. Cannon said the chase was appropriate, though acknowledging he shouldn’t have slapped the suspect.

State police officials, however, said the 30-minute chase and the number of deputies involved posed a greater danger than a single traffic violator warranted.

Their probe pointed out nine policy breaches and possible law violations.

If a seasoned officer like Sheriff Cannon can lose his self-control after chasing a traffic violator, it is easy to see how a less experienced officer like Mr. Shelton, who became a deputy two years ago, could lose his cool after chasing a man suspected of being the gunman in a recent shooting. He was wrongly suspected, as it turned out, but he was wanted on a charge of running into his girlfriend with his Kia. And he did flee police.

So while the deputy’s response might be understandable, it is not acceptable. Law enforcement officers must conform to higher standards of behavior even in the most stressful circumstances. Mr. Shelton’s superiors should not make excuses for his irresponsible, risky actions — no matter how much they empathize with him. This time, no one but the suspect was hurt. But the deputy’s behavior could have led to more serious injuries or even deaths.

And while they are considering how to discipline Mr. Shelton, police authorities would do well to review their policies regarding car chases. Pursuing a fleeing suspect from, say, a bank robbery might warrant a chase. But it is difficult to justify endangering lives and property in a high-speed chase to catch a speeder.