It is a tragedy that is incomprehensible.

Many parents in Ottawa said finding the words to explain to their kids why a gunman would open fire in a school and kill more than 20 people is nearly impossible.

"I don't know how to tell them,” said parent Melanie Finney. “I think it could shatter their childhood."

“As a parent I can't describe how it makes you feel for sure, it brings tears to your eyes,” said Barry Wood.

Psychotherapist Marion Balla said parents should talk to their children about it in a simple way and let them ask the questions.

She said relating it to a loss of a grandparent or pet may be helpful.

“Tie that together because you've already started educating your children around this, you link it, you say 'these little children are gone to where grandma went or our little pet’," Balla said.

But some parents insist their kids are too young to hear about it.

“There’s no point in discussing that with them…just would confuse them and make them sad,” said Wood. “Like I said, my oldest is only seven years old,”

“I should talk to them about it but I’m a bit reluctant to because of the fear it would provoke," said Judith Tait, who has taught in the United Kingdom and Canada.

She said this incident raises concerns about school safety.

“It is likely something to happen in Canada? I’m not sure, but it would make me feel safer as a parent if the schools had more security,” Tait said.

Balla said no one will ever fully understand why this tragedy occurred.

“We're not talking denial here, we're not talking pretend, but this is something a child has to somehow take in and make sense of a senseless act and we're not going to be able to do that,” Balla said. “There’s no way to rationalize this.”

With a report from CTV Ottawa’s Katie Griffin