New York (CNN) -- Things a 7-year-old boy expects Mom to put in his backpack: A peanut butter sandwich. Pencils. Maybe even a nice note with a little heart scrawled on it.
Things he doesn't: a flare gun, a .22-caliber pistol, a loaded magazine and, for good measure, 14 more bullets in a plastic bag.
But that's exactly what a second-grader had inside his Batman backpack Thursday morning when he arrived at Wave Preparatory Elementary School in Far Rockaway in Queens, Police Deputy Commissioner Paul Browne said Friday.
The mom, Deborah Farley, 53, told police she had been, according to Browne, "out walking the streets of Queens late Wednesday night" with the guns in her son's backpack and she forgot to take them out.
She rushed back to school after dropping him off Thursday and asked the boy what he'd done with the gun, Browne said.
When the boy told her he'd handed it over to a classmate, she finally came clean to administrators, who put the school on lockdown and called police.
As it turns out, the boy had given away the flare gun, but police found the pistol, the loaded magazine and the bag of bullets still in his bag, according to Browne.
Nobody was hurt, but police arrested Farley on Friday on charges of endangering the welfare of a child and criminal possession of a firearm. The pistol was unlicensed, Browne said.
A search of the woman's home found more ammunition and seven plastic bags of marijuana, Browne said.
Child protective workers took the boy and his 9-year-old brother into custody, he said.