New Jersey turned his gun in cold blood on two "good friends" over a drug deal, prosecutors said.
"We believe this is tied to a drug transaction," Bergen County Prosecutor John Molinelli said, referring to the dead men as "good friends" of Kiriakakis.
They found a stun gun and illegal prescription drugs, but it was unclear whether the murder weapon was recovered.
Kiriakakis' neighbors in Auburndale, Queens, said animal-care authorities visited his home several times to check on his two German shepherds.
"He wasn't well-liked on the block," said Janine Menoutis, 31. "He rubbed people the wrong way."
Kiriakakis' bar, Pearl Restaurant and Lounge, had a reputation as a drug-friendly hangout, local merchants and bargoers said.
"All the neighborhood cokeheads go there," said a bartender at neighboring Cue Bar.
"Nick's a good guy and he runs a respected establishment," countered a bar worker.