As the Trump administration advocates for more guns in schools and allowing teachers to carry firearms, two separate incidents in Virginia and California on Tuesday in which trained school employees accidentally fired their weapons highlight the dangers of such a proposal.

A teacher who is also a reserve police officer trained to use a gun accidentally discharged a firearm at Seaside High School in Monterey County, California, on Tuesday. According to the local outlet KSBW, Dennis Alexander’s gun went off around 1 pm while he was teaching a course about gun safety. He was pointing his gun at the ceiling when it went off, and pieces of the ceiling hit the ground.

The local police department said no one suffered serious injuries, but one 17-year-old boy was harmed when fragments from the bullet hit his neck, the boy’s father, Fermin Gonzales, told KSBW. The boy’s parents only figured out what had happened when he returned home from school with blood on his shirt and bullet fragments on his neck.

“He’s shaken up, but he’s going to be okay. I’m just pretty upset that no one told us anything and we had to call the police ourselves to report it,” the father told the TV station.

In a separate incident in Alexandria, Virginia, on Tuesday, a school resource officer — a five-year veteran of the Alexandria Police Department — accidentally discharged his weapon while inside George Washington Middle School. No one, including the officer, was injured.

“I just think it was an accident that happened, and we’re going to investigate it and find out, and we’re going to move forward,” Capt. D.C. Hayes told NBC Washington.

The thing about good guys with guns is that they can be dangerous too

The White House on Sunday unveiled its plan to combat school shootings following the mass shooting in Parkland, Florida, in February that left 17 people dead. Among its proposals is renewed support from President Donald Trump to arm teachers and other school employees.

The president on Twitter said he believes arming teachers will serve as a “deterrent” to potential shooters.

Very strong improvement and strengthening of background checks will be fully backed by White House. Legislation moving forward. Bump Stocks will soon be out. Highly trained expert teachers will be allowed to conceal carry, subject to State Law. Armed guards OK, deterrent!....... — Donald J. Trump (@realDonaldTrump) March 12, 2018

Education Secretary Betsy DeVos said in an interview with 60 Minutes aired on Sunday that giving teachers guns in the classroom “should be an option for states and communities to consider.” Trump’s daughter and White House adviser Ivanka Trump, in a February interview with NBC News, said that arming teachers “needs to be discussed.” (The National Rifle Association supports arming teachers too.)

Tuesday’s incidents, in which two trained individuals accidentally fired their weapons, highlight the dangers of putting more guns in schools. As Vox’s German Lopez recently pointed out, there is no good research on the effect of arming teachers or the effect of putting more armed police or security in schools.

Adults with guns in schools sometimes fire them accidentally

Incidents like the two accidents on Tuesday have gotten more attention now that the Trump administration has proposed arming some teachers, putting more guns into school buildings. But they aren’t necessarily new — many incidents from the past suggest that putting guns in schools can lead to accidental shootings and even occasional injuries and deaths.

Everytown for Gun Safety, a gun control advocacy group, collects reports school shootings — including gunshots in a school or at a college that were fired accidentally, or cases in which no one was injured. Matching Everytown’s database to local media reports shows that in the past month alone, three guns belonging to adults were fired in school buildings:

A Georgia high school teacher barricaded himself inside a classroom and fired a bullet into a window.

A sheriff’s deputy in Florida shot himself while responding to a false alarm about school gunfire.

A third-grader in Minnesota accidentally fired a school police officer’s gun.

Three of these accidental shootings in one month is relatively high, although it’s not clear if that’s simply the result of increased reporting because Everytown’s database is based on local media reports.

Still, this has happened before with some regularity. In 2016, a sheriff’s deputy fired his gun in a Michigan high school while testing a robotics machine, hitting a teacher in the neck, and a part-time correctional officer at an elementary school for a job interview at a Florida elementary school shot himself in the knee. In 2014, a teacher in Utah accidentally shot herself in the leg (and shattered a toilet) while at school. In 2013, a police officer assigned to a New York high school after the Sandy Hook shooting accidentally fired his weapon in a hallway.

This adds to the evidence that putting more guns in schools could actually make gun violence worse: The problem in the US is that there are so many guns in circulation, which makes it easier for conflict to escalate to gun violence — or for guns to be mishandled and kill or injure bystanders.