DALLAS (CBSDFW.COM) — Dallas ISD is investigating after a 5-year-old kindergarten student was able to walk off campus at Highland Meadows Elementary last week.

The 5-year-old’s mother, Jenniffer Castaneda, said she didn’t know how her daughter got out.

“I was really shaking. I was really, really upset.” Castaneda said.

Everyday, Castaneda walks two blocks with her daughter, Alessia, to school.

Last Thursday, she said Alessia walked back in the middle of the day alone.

Showing up at home without warning, she surprised her grandfather when she rang the doorbell.

“My dad said he opened up the door,” Castaneda said. “And he heard somebody crying.”

Castaneda said her daughter explained she had raised her hand in class to go to the bathroom, but her teacher wasn’t paying attention and she had an accident.

“She said that he came up to her and he was like, ‘Clean it up’,” Castaneda said.

Thinking her teacher was upset, Alessia said she felt sad.

A Dallas ISD spokesperson confirmed, contrary to school policy, that Alessia was sent to the bathroom by herself and managed to leave campus.

The district said security camera footage showed she was off campus for 20 minutes. They also told CBS 11 the school was aware a student was missing and was actively searching for her when she re-appeared with her mother.

The district said, it held a campus wide safety meeting Monday following the incident to remind staff of existing policies and to implement several new ones.

As part of its investigation, it is also looking into employees’ actions.

Castaneda said her family is still upset thinking how many ways this story could have ended.

“There were so many things that could have happened to her, from being run over by a car, kidnapped…Anything could have happened,” she said.