But Borelli testified that Armento pulled the gun on him, while Brancato watched, minutes before the shooting on Dec. 10, 2005.
The two had dashed to Borelli's house after trying to break into a nearby Bronx apartment looking for drugs to steal, said Borelli, 53, who said he had been Brancato's heroin and crack dealer.
"Armento came out like this, with a gun - with a pistol," said Borelli, adding that he chased Armento away with an ax handle.
Prosecutors say Brancato and Armento then returned to the apartment, where Officer Daniel Enchautegui - who lived next door - confronted them. Armento shot Enchautegui, who fired back and wounded both men.
Armento has been convicted of first-degree murder and sentenced to life in prison without parole.
Defense lawyer Joseph Tacopina has acknowledged Brancato was a "strung out" drug addict. But Tacopina has said the former actor never intended to hurt anyone.
Tacopina has portrayed Borelli as a liar looking for leniency in his own legal troubles.
Brancato, 32, made his 1993 debut in "A Bronx Tale" opposite Robert De Niro. He has appeared in more than a dozen other movies and played a doomed aspiring mobster in HBO's "The Sopranos."