Angelo Bracco, his sons Christian and Eric, and Dominick Barbera pleaded not guilty on Friday in Brooklyn Supreme Court to gang assault charges stemming from the death of 17-year-old Sharif Abdallah.

Abdallah collapsed and died in March after police and witnesses say he and the four suspects got into a fight in Prospect Park. The medical examiner said Abdallah had a pre-existing heart problem which escalated after the fight, ruling his death a homicide.

"When he was chasing our clients, he collapsed, so that's why we do not agree with the conclusion of the medical examiner that this is a homicide. We believe other factors contributed to his death," Defense Attorney David Epstein argues.

Abdallah?s family and friends disagree with Epstein?s statement, saying that "it doesn?t matter what pre-existing condition he had, he was beaten to death."

The district attorney?s office did not upgrade the charges, saying the grand jury evidence supports the gang assault counts.

The next court date is July 2. Officials say if the defendants are found guilty on the gang assault charges, they face up to 15 years behind bars.