It’s no secret that SEPTA chief Thomas Nestel is active on Twitter. The transit authority’s top cop routinely tweets out entertaining reports of fare-jumpers and festive well-wishes to law-abiding passengers from his account, @TNestel3.

On Sunday night, though, Nestel received a gravely serious tweet from a citizen reporting intravenous drug use on the Market-Frankford Line. Within minutes, SEPTA cops were on the scene.

“It was a 30-year-old Philly resident,” Nestel told Metro about the suspect. Nestel’s officers “stopped him, frisked him for safety due to the report of hypodermic [needle] use, did a field interview, offered medical assistance which was declined, and told him why he had been stopped.”

Nestel said the suspect “denied any drug use” but that he showed telltale signs of intoxication. “His pupils were pinpoints and did not react to light,” Nestel said.

The concerned citizen who sent Nestel that tweet spoke with Metro on the condition of anonymity.

“I just thought it was a pretty absurd thing for him to be doing in plain sight of other riders and potentially children,” the man explains. He says that Nestel’s routine friendliness and accessibility gave him the idea to report the incident.

“I heard Chief Nestel speak at a neighbors’ association meeting once,” the man said, “and he seemed very plugged into social media, so I figured, ‘Why not?’”

The concerned citizen added that he figured “police would be able to at least point him in the right direction for some help.”

It seems that’s exactly what Nestel has in mind, too.

“We do not receive many calls from riders reporting drug use,” Nestel explained. “Something that I always keep in the back of my head when we do receive a call about someone unconscious or appearing to be drunk or high is, ‘Would I rather they have been behind the wheel of a car?’”

The chief went on to say that “maybe they made some bad decisions getting in the condition they are, but maybe they made a good one, too” by not driving.

“I was really amazed by how rapid the response was,” the good Samaritan says about his tweet  report to Nestel.

For their part, SEPTA cops are going to check the security video to see if the man was shooting up on the subway line as was reported.

“After that, we will decide how to proceed. The goal will be to get him in rehab,” Nestel concludes, “and if that requires an arrest, then we may pursue that avenue.”