A gun seized by D.C. police in Ward 7 in 2016. (Courtesy of D.C. Police)

Phil Mendelson, a Democrat, is chairman of the D.C. Council.

Last year, homicides in the District were up 38 percent. There were 160, compared with fewer than 90 in 2012. Yet violent crime overall has been declining year after year. Last year, assault with a dangerous weapon was down 10 percent. The difference between assault with a dangerous weapon and homicide can be a matter of inches.

What gives?

The answer lies in the lethality of assaults. Rather than fists or knives, people are using guns. And rather than firing one or two shots, criminals are using large-capacity magazines to fire dozens — or even scores — of rounds. The more shots fired, the more likely a kill.

Criminals make two choices: to commit a crime and what weapon to use. Typically, law enforcement focuses on the crime. But if we want to reduce gun violence — and the lethality of crime — we also should focus on the second choice.

The criminal code makes the distinction. All violent crimes, when using a gun, carry an enhanced penalty. The penalty for robbery, for instance, is two to 15 years. If a gun was used, however, the sentence carries a mandatory minimum of five years.

It may be off-putting to say this, but we’ve become too tolerant and too complacent about murder in our community. We have to be different.

To stop the shootings, we are going to have to change behavior. And to change behavior, we are going to have to do something different. Such as focus on guns.

To change behavior, the government has got to get criminals to think twice before carrying or using a gun. The government can do this by pulling the levers it has and doing so as a coordinated and publicized strategy.

It is not enough that the police have a gun recovery unit. There should be a gun prosecution unit and a gun court. Experience in other jurisdictions shows that this can lead to higher conviction rates and quicker convictions.

It is not enough that the criminal code carries enhanced penalties for using a gun in connection with a crime. This is not well known outside government and, typically, the enhanced penalties are given up in plea bargaining. But a different message would be sent if the penalties were applied.

The same message — that the choice to use a gun will not be tolerated — would be sent if all supervising agencies, including the Parole Commission and the Court Services and Offender Supervision Agency, acted differently, more swiftly, to impose sanctions when dealing with a gun offender.

The point is that the government is not doing an effective job of sending that message. To reinforce the message, all areas of law enforcement — from police to courts to prison to supervised release — must focus agency resources on targeting gun offenders. And this means that the response from every agency to gun-related offenses and gun offenders must be swift and certain.

The message is meaningless unless backed up. Backing it up means using every sanction legally available to the agency.

To be an effective strategy, every agency must do this together, each in its own way.

The sum will be even greater than its parts if the coordinated campaign is publicized. A public relations campaign is critical. Sending a message that guns will not be tolerated, backed up with every agency pulling the levers it has, will get criminals to think twice. That will reduce gun violence.

And to reduce homicides, we need to reduce gun violence.

Last year, New York City, with a population of more than 8.5 million people, had 289 homicides. Last year, the District, with a population of 702,000, had 160 homicides.

We can do better.