Drug-unit cops conducting routine surveillance in East Somerville followed a person they knew from previous investigations to a pair of percocet dealers July 9, police said

Dennis Ryan, 32, of 24 Spring St., Everett, and Charles Ryan, 55, of 75 Myrtle St., allegedly met the man and sold him four pills of the prescription painkiller.

Charles Ryan was arrested and charged with distribution of a class B drug, conspiracy to violate a drug law and possession of a class B drug with intent to distribute. Dennis Ryan was arrested and charged with conspiracy to violate a drug law.

After the hand to hand transaction, the buyer was stopped by investigators and agreed to answer questions, police said.

Dennis Ryan and Charles Ryan were stopped by investigators as they tried to get back home to Myrtle Street, police said.

A search of Charles Ryan allegedly revealed 21 more percocet pills. The pills were stored loosely inside of defendant Charles Ryan’s left front pants pocket, police said.

Once arrested, Charles Ryan allegedly made incriminating statements.