When the sheriff in Franklin County, Ky., posted a flier on Facebook asking local drug dealers to snitch on their competition, the response was more than a little incredulous.

That is, until a tip sent to a phone number on the flier led to an investigation that helped the sheriff arrest a local drug dealer. The authorities recovered crack cocaine, cocaine, four pounds of marijuana and four firearms, the sheriff, Pat Melton, said on Thursday.

“Everything proceeded pretty rapidly on it,” he said in a phone interview.

It’s a comical tactic with serious results: “We offer a free service to help you eliminate your drug competition!” Under a large marijuana leaf, the flier contained a blank form encouraging drug dealers to identify the competition and provide contact information. It also asked respondents to identify the hours the competition was most active.

The original post reached viral proportions when the rapper Ludacris posted on Instagram about it. The department then put his Instagram post on Facebook, and replied to the rapper.