Maybe it's too much "Paw Patrol" or maybe its innate. Either way, Ethan Hierro has wanted to be a police officer since he was 3 years old.

"He really is always arresting everyone in the house and putting us in jail, and it’s really just Ethan," said Isabel Estevez, the 5-year-old boy's mother.

Hierro's wish came true when he became a Tarrytown police officer on Tuesday with an official swearing in ceremony.

About 16 months ago, Ethan was diagnosed with glioblastoma, a form of brain cancer with no cure.

"He's so young and so little to be going through all of this but he’s so strong and brave," said Hierro's sister, Eva.

The Tarrytown Police Department did something it's never done before: granted a wish.

"We went and found a uniform online that we purchased for Ethan and we had our patches put on the sleeves by a local tailor," said Tarrytown Police Chief John Barbelet.

They picked him up for his first day of work with a procession of police cars.

"He sat at the desk and dispatched some calls," Barbelet said.

Hierro and his mother have to regularly travel to Tennessee for treatment.

"When I don't see Ethan playing or something or my mom seeing her in the living room, it just feels like something's missing," said Ethan's sister, Abby Hierro.

Estevez is a single mother, who had to stop working so that Ethan can continue his treatment.

She created a fundraiser to help pay for her son's treatment.