A southwestern Ohio sheriff unveiled a billboard campaign calling out school districts he says are not moving fast enough to make safety upgrades to protect students and staff from mass shootings.

His first target was Hamilton City Schools. The sheriff said he went after Hamilton first because he considers their district one of the worst.

"Because I believe it may be one of the least secure and least transparent of all the school boards," he said in an interview. "And, I don't believe they've done enough or are doing enough, and I don't believe they're transparent at all, with what they spend their money for. And they should spend money now, to make it more secure."

The sheriff said more billboards are coming to draw attention to other districts who are not doing enough to increase security in light of mass shootings at schools in Parkland, Florida, and Santa Fe, Texas.

Jones was one of the first elected officials nationally to call for arming teachers in schools and made national news earlier this year when he offered free firearm instruction for them and other school staff.

He had to cap it off at 300 when 250 signed up in less than 24 hours. To date, 150 school personnel have been trained, he said.