LINCOLN -- They teach martial arts to youth in downtown Lincoln, but this week, two men listed as founders of the STKD Tae Kwon Do studio, Brandon Cronkhite and Joshua Szlachciuk, were arrested.
They're accused of mailing thousands of dollars worth of marijuana products out of state.
"There were several parcels that were leaving that location and being shipped across the country to Florida and Tennessee," said Lt. Troy Minton-Sander with the Placer County Sheriff's Office.
Jeff Perry owns the coffee shop next door to the studio which opened just a few months ago.
"It's really scary when you don't even know," Perry said.
He's surprised hearing men who teach children to protect themselves are in trouble with the law.
"I had no clue, they just kind of, they go over there, I see a lot of people coming in and coming out. I've dealt with one of them, he was really nice," said Perry.
With help from the U.S. Postal Service, the Placer County Sheriff's Office launched an investigation in July, following complaints about a marijuana grow on Wise Road in rural Lincoln.
"We were able to determine what appeared to be a legal operation appeared to be something that had some criminality behind it, and based on that we were able to write a search warrant," said Lt. Minton-Sander.
Tuesday investigators arrested Cronkhite and Szlachciuk for numerous felony drug and weapons charges.
Investigators recovered 60 plants, 65 pounds of processed marijuana and concentrated cannabis, plus several illegal assault weapons.
Investigators say both the suspects lived on the property in rural Lincoln.
It's the same address where a 3 and 5-year-old boy died in an ATV crash in April 2015.
Following that accident, Brandon Cronkhite was identified as the father of one of the boys who crashed into a pond on the property.
On the Tae Kwon Do studio's website, Szlachciuk is described as a third-degree black belt who served in the Army.
The Placer County Sheriff's Office is still looking for a third person of interest, Stephen Starner.