She has already paid to replace the toilet, which school officials have said cost roughly $200.
In court papers, city prosecutors say Ferguson-Montgomery discharged her 9mm handgun inside a Westbrook Elementary School restroom on Sept. 11, leaving a live hollow-point 9mm round in front of the toilet and an expended casing in the adjacent stall. A blast pattern from the shooting indicated the weapon had been fired from above the toilet and from right to left, as if the person had been facing toward the bathroom stall's door.
City prosecutors say Ferguson-Montgomery initially told police the gun had fallen from a hip holster and accidentally discharged. The Tooele resident later admitted to removing the weapon from its holster and placing it on top of the toilet paper dispenser.
"The defendant stated that she did not remember pulling the trigger, but conceded that is what likely happened," Granite School District police Det. Randy Porter wrote in affidavit supporting the charges.
Ferguson-Montgomery suffered injuries to her left calf, possibly from bullet fragments or pieces of the damaged toilet, Granite School District spokesman Ben Horsley said. No one else was injured.
Ferguson-Montgomery is a concealed weapons permit holder and under Utah law is allowed to carry her handgun at school. She quit her job as a sixth-grade teacher after the charges were filed. District officials also have said Montgomery was disciplined for violating an unspecified district policy, but had been cleared to return to the classroom prior to her resignation.
Asked about the nature of the incident on Wednesday, city prosecutor Tracy Cowdell agreed with a news reporter that it was "kind of funny."
But he added: " ... It is also serious. There's a lot of debate about guns and where they are appropriate. But they can't be going off at school we can all agree on that."
Ferguson-Montgomery's attorney, Douglas P. Hoyt, declined to comment.
It's not clear how many Utah teachers carry concealed weapons on campuses. Gun rights advocates estimate that statewide about 1 percent of all teachers or 240 individuals are concealed weapons permit-holders.
Utah teachers are allowed to carry guns, but the weapons must be completely concealed and kept with the teacher at all times, including inside a bathroom stall, according to the state office of education. Teachers are not required to tell the school that they have a gun.