Twelve men accused in the brutal slaying of 15-year-old Lesandro Guzman-Feliz, known as Junior, pleaded not guilty before a judge Wednesday.

The twelfth and likely final suspect, Luis Cabrera Santos, 25, arrived in New York a day earlier after extradition from Connecticut, where state police arrested him last week. The others were arrested in New York and New Jersey.

Six of them face charges of second-degree murder, and six of first-degree murder.

As guards escorted two of the suspects out of the courtroom, Guzman-Feliz's mother, in Spanish, "Killers!"

Investigators say the group of men -- all suspected members of the violent Trinitarios gang -- hacked and slashed Junior to death outside a Belmont bodega on June 19.

Graphic surveillance video of the attack circulated widely on social media, prompting outrage, demands for justice and condemnation in New York City and beyond.

The 12 men are due back in court on Oct. 25.