A reward sign and messages of sympathy are posted in Chicago on Nov. 4, 2015, after the shooting death of 9-year-old Tyshawn Lee. (Teresa Crawford/AP)

Lori Lightfoot, a Democrat, is mayor of Chicago.

Recently, I got into a bit of a “conversation” with Sen. Ted Cruz (R-Tex.) on Twitter about our nation’s gun laws and how to best protect our citizens from violent crimes. If the past three years have taught us anything, however, it’s that governing and debating via social media does not solve most problems. So rather than hashing this out 280 characters at a time, let me expound here: Maybe Cruz will listen to what I’m trying to say.

Cruz suggested that big-city mayors like me should “put aside the partisan talking points & the failed gun-control policies Chicago has pursued for decades,” including efforts to look at the flow of guns beyond state and city boundaries, and “Instead, lock up the violent criminals who are committing murder … [and] PREVENT felons & fugitives from illegally buying firearms.”

Put that way, it almost sounds as though the senator agrees with me that the most useful thing we can do as a country right now is to make it significantly harder for people to get their hands on illegal weapons. But in taking a swipe at my tweet about the scope of the problem, he missed the point.

Sixty percent of firearms owned or used illegally recovered in Chicago come from outside Illinois. These guns don’t recognize state lines or city boundaries. Cruz said the five U.S. cities with the highest murder rates “have had Democratic mayors for decades and aggressive gun control policies — none seems to be working.” He’s making my case for me: As long as people can drive from Illinois to Indiana and purchase a personal arsenal without a background check, Chicago’s gun laws will always be as weak as those of the closest permissive state.

The consequences of this situation are deadly. A gang member from Chicago bought at least seven illegal guns from someone in New Mexico. Two of those guns were used to commit homicides in the city, including the execution of a 9-year-old boy, Tyshawn Lee, in 2015. Tyshawn’s death was preventable.

These aren’t the only guns we have traced from crime scenes in Chicago. We know which federally licensed gun stores in Illinois and Indiana sell a disproportionate share of the guns that end up on our streets, but national politicians continue to look the other way and do nothing to stop them.

Here in Chicago, we take our ­gun-violence problem very seriously. It remains unacceptable to me and to the overwhelming majority of our residents that there are neighborhoods where it is nearly impossible to find young people who have not been personally affected by gun violence.

It is our highest priority to rebuild communities that have been harmed for generations by disinvestment, racism and gang violence. We’re making gradual, but critical, progress. After a particularly difficult few years, innovative policing strategies and active, dedicated community leaders are hopefully starting to turn the tide. In fact, this August Chicago saw its lowest numbers of shootings and murders in any August since 2011. And murders for the summer are down almost 24 percent from the previous summer.

But it’s not enough. We urgently need help at the federal level to stop the flow of weapons that turn conflicts lethal. We need to close the loopholes that allow people to purchase deadly weapons without a background check. We need to end the proliferation of assault weapons, which exist only to inflict maximum damage on large groups of people. And we need to enact strong anti-trafficking laws and to enforce them. We need leaders who will listen to us and work with us, not just use our city as a dog whistle at country-club fundraisers and conservative political conventions.

So Sen. Cruz, if you’re actually interested in learning about the struggles we’re facing, come to Chicago. And listen — really listen — to our mothers and fathers, our pastors, our teachers, our police, our prosecutors and our children as they tell you how gun violence has irrevocably changed their lives. Talk to them as people, not just as “Democrats” or a rhetorical device.

But don’t you dare lecture us with half-truths, cherry-picked statistics and debunked rhetoric designed to score political points with your base and your donors while you, Senate Majority Leader Mitch McConnell (R-Ky.) and the other Republicans in charge of the Senate sit in dereliction of your duty day after day, shooting after shooting.

Chicagoans are dying, Texans are dying, and communities across all of America deserve an honest debate and real action. The stakes are too high to continue business as usual.