"We said, 'Hey, do you mind, just drive by, flash your lights, take a couple of pictures,'" his mom Katy recalled to KLTV.
The officers did much more than that, however. They showed up with a SWAT vehicle, in addition to several officers in their cop cars.
Aside from Mason's love of crime-fighting, the officers had another reason they wanted to make his day special. His baby sister, Ellie, had spent two months in the NICU.
"He had a really hard time. He didn't get to see her," Katy said of Mason.
The family was grateful for the sweet note, gift cards and goodies the officers left, but also for giving Mason a birthday he'll never forget.
"When somebody does something nice for you, it's something," dad Aaron said. "But if somebody does something nice for your child, it means a whole lot more."
Read more about this story from KLTV.