He felt at a loss after Friday's shooting in Newtown.
"That following Monday was one of the hardest days of my life," Vejrostek said. He has two kids at Imagine Charter School in Firestone.
He says he saw other reports of Marines standing outside of schools and wanted to do the same.
On Thursday, parents kept stopping to thank him for making them feel safe.
Technically, the Marines have very specific rules about when retired Marines are and are not supposed to wear their uniforms, and standing guard at schools doesn't qualify.
But Vejrostek sees it differently.
"As far as I'm concerned I am on duty," he said. "It's letting these kids know that there are people here that love them and will protect them."
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