President Trump should meet Joe Zamudio. That was my first thought as I sat in a Southern California high school watching Trump suggest that teachers like me should carry guns. Seven years ago, I was a radio reporter in Arizona standing in a blood-soaked parking lot interviewing a shaken man who had just witnessed a massacre. Earlier that day, Joe Zamudio had been legally carrying his 9 mm pistol when a mentally ill man named Jared Loughner opened fire, killing six and severely wounding others, including Congresswoman Gabrielle Giffords. In that moment, Zamudio had a split-second decision to make: Does he fire at the man with the gun?

As he told me, the Los Angeles Times, and other reporters, Zamudio quickly zeroed in on a man holding a Glock pistol. Yet, Zamudio decided to take his finger off the trigger and tackle the man who was waving the gun. As he grabbed him, people in the crowd started shouting that he had the wrong guy.

Seconds earlier, the man with the gun had wrestled the pistol away from Loughner. Zamudio would have shot an innocent man.

Now that I’m a teacher, I’ve broken up fights and I’ve stopped fights from starting. Thankfully, I’ve never faced an armed student. But I’ve considered that possibility. When I look around most classrooms, I see folding partition walls, single-paned windows, and unlocked doors. These make schools vulnerable to shooters, but they also make students vulnerable to teachers with guns.

I will never have a gun in the classroom, and if required to, I would resign.

Since I was a teenager, I’ve shot many kinds of guns: handguns, shotguns, rifles—and an AR-15. They each have different characteristics, but they’re all capable of piercing a typical high school wall or window. If teachers are armed, all of those teachers must be able to instantly think like Joe Zamudio: Will my bullet hit the right target? Is that person who is waving a gun around the shooter, or could it be the person who just pulled the gun out of the shooter’s hand (like in Tucson)? What if I miss? Where does the bullet stop? How many of those skinny walls and windows will the bullet pierce before it drops? If I’m firing a high-powered gun, will the bullet pass through the shooter and hit another student? And will the police think I’m the shooter if they see me with a gun?

These are not hypotheticals. These are real considerations trained police officers face when dealing with active shooters. But teachers aren’t cops. Even with the cursory gun training some politicians have suggested, teachers would lack the real-world experience of a full-time officer. Police also keep their guns secured—another aspect of their training. If, let’s say, a million teachers have guns, how many will be left unsecured by irresponsible teachers? If it’s even 1 percent, that means 10,000 handguns could be near the reach of children every day.

I have great respect for responsible gun owners. When used properly, guns can protect families and help kids bond with their parents during hunting or shooting trips. My own sons shot their first .22 rifle when they were little. They also learned the immense responsibility that comes with even touching a firearm. Teachers also have a great responsibility: to teach, mentor, console, inspire, and, yes, to protect.

Seven years ago in Tucson, the shooter was brought down with a folding chair and the hands of brave citizens. Thankfully, no one accidentally shot an innocent bystander. But a million teachers with guns can’t all be as perfect as Joe Zamudio.

Kevin Tripp was a radio, TV, and print journalist for 20 years before recently earning his social studies teaching credential in Orange County, California.