Feeley initially took the photo to send to her husband because she thought her daughter was being "mischievous" by standing on the toilet.
It was only then Chandler explained to her mum that she was practising what she had been taught to do if you are trapped in a toilet when a gunman attacks.
Feeley said: “At that moment all innocence of what I thought my three-year-old possessed was gone.
“Politicians take a look. This is your child, your children, your grandchildren and future generations to come. They are barely three and they will hide in bathroom stalls.”
The mother continued: “No one thinks gun control will be 100% crime control. But maybe, just maybe, it helps 1% or 2% or 50%? Who knows unless we try? Why on earth are there not universal background checks?
"Where is a universal registration database? Why are high capacity magazines ever permitted to be sold to anyone other than direct to the military?”
One commenter Roger Cox, a teacher from Illinois, explained that he has participated in drills in preparation for a gunman.
“As a teacher I have been through many lockdown drills," he wrote. "We do ‘live shooter drills’ when children aren't present. The shots in the hallway are muffled and quiet, not loud and alarming as most would believe.”
“Teachers are forced to make a decision for their students... make a run for it and hope nobody is standing outside waiting or stay put and hope that law enforcement arrives and can contain the situation in minutes.”