Vincent Arcona, 27, was hit with drug charges and is being investigated as a possible accomplice in a fatal Midtown shooting. View Full Caption NYPD

MIDTOWN — The suspect believed to be involved in a fatal shooting during a failed bid to take over the drug trade in a Manhattan McDonalds snorted drugs in a precinct interrogation room from a bag he pulled from his own butt on Saturday, authorities said.

Vincent Arcona, 27, snorted the drug and threw the bag on the ground, before admitting to Midtown South Precinct Detective Adrian Calemmo that the bag was full of heroin, according to an affidavit.

Arcona, who has yet to be charged with the Nov. 9 shooting near Penn Station during the morning rush hour, was arrested on drug possession and tampering with evidence on Saturday, according to the Manhattan District Attorney's office.

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The suspected gunman in the case, Franciso Alsina, 23, who was arrested in Rhode Island on Nov. 13, was still awaiting extradition Monday afternoon, according to Rhode Island state police.

Authorities believe that Alsina and Arcona hatched a plot on Nov. 9 to move in on the drug territory in the fast food restaurant. Alsina fatally shot Angel Quiñones, 43, and wounded William Lamboy, 45, and Ed Torres, 48, when they refused his offer, sources said..

Quiñones, the father of a 13-year-old boy, was pronounced dead in the A C E station. The other two victims were rushed to the hospital.

On Nov. 12, Arcona was arrested when he turned up at Bronx-Lebanon Hospital trying to pick up medication under a phony name, and then tried to use a benefits card with his own name, sources said.

He is being held at Rikers Island on $25,000 bail and he is due back in court on Nov. 18, records show.

Arcona's lawyer Mitch Schuman from New York County Defender Services reinforced that his client had not been charged with homicide and declined to further comment on the case.