A keenly observant Drug Enforcement Administration agent is being credited with the take-down of a Johns Creek cocaine trafficker that led to a 17-year federal prison sentence announced Thursday.

The agent was off duty and waiting to have his car emissions tested at a gas station on Cheshire Bridge Road two days before Christmas in 2013 when he spotted Ricky Nuckles, 41, park his car at a gas pump, go inside the station’s convenience store and place a call on his cell phone, according to U.S. attorney John Horn.

Moments later, another car parked next to Nuckles’ vehicle, Horn said in a release. A man got out and placed a large suitcase inside Nuckles’s car, then drove away as Nuckles locked the door of his car remotely, according to the federal prosecutor.

As Nuckles tried to go to his car, the agent, who was not identified by the U.S. attorney, confronted him and identified himself, and the agent told him what he had witnessed. Nuckles ran back inside the store and quickly ditched his cell phone, Horn said.

When Nuckles came back outside, the agent was still waiting by the car. Learning that there was a loaded firearm next to the driver’s seat in the car, the agent placed himself between Nuckles and the car and dialed 911. More DEA agents and Atlanta police officers arrived, and Nuckles agreed to a search of the suitcase, Horn said.

Agents found cocaine, which had a wholesale value of about $750,000, and a handgun, Horn said.

“Thanks to a vigilant off-duty DEA agent, 22 kilograms of cocaine is off the streets, and Nuckles’ drug-trafficking days are finished,” Horn said.

Nuckles was found guilty by a jury on May 13, 2015. On Thursday, he was sentenced to 17 years and 7 months in prison for trafficking 22 kilos of coke while possessing a firearm.

His prison term is to be followed by five years of supervised release.