According to TMZ, a third person was arrested in connection to Mac Miller's overdose death last year. 

L.A. law enforcement confirmed that Stephen "Stevie" Walter was arrested on Monday (September 23) on a charge of conspiracy to distribute a controlled substance. Walter is currently on supervised release following a 10-year federal drug trafficking sentence.

Authorities say Cameron James Pettit, who was arrested last month, contacted Walter to obtain ten Percocet pills for Mac Miller. Walter then sent a runner, believed to be Ryan Reavis, to deliver the pills to Pettit. Reavis was arrested in Lake Havasu this week and police say they found firearms, prescription pills, and a prescription pad in his home. 

Source: TMZ