A seafood delivery driver has been accused of stabbing a man during a daytime fight that prosecutors say erupted over a woman.

Kemar K. Downer, 39, a Jamaican-born employee at Sayle's Seafood, is charged with two counts of assault and battery with a dangerous weapon causing serious bodily injury after Tuesday morning's confrontation.

The incident left the man with serious stab wounds requiring multiple surgeries.

Downer's attorney insists his client acted in self-defense, telling a Nantucket courtroom the violence began when the alleged victim attacked him from behind without warning in an altercation that 'had something to do with a girl.'

Downer pleaded not guilty during his arraignment Wednesday in Nantucket District Court before Judge James Sullivan, who released him after he posted $2,500 bail despite prosecutors seeking $10,000 and GPS monitoring.

The judge imposed GPS monitoring, ordered Downer to have no contact with the alleged victim and barred him from going near the man's home.

The Cape & Islands District Attorney's Office charged Downer after police found a man lying on the sidewalk bleeding from stab wounds to his chest and forearm following the confrontation on South Beach Street shortly before 10:30am on Tuesday.

The violent confrontation has stunned Nantucket residents, where serious violent crime is extremely rare.

The stabbing shattered the calm on Nantucket, where violent crime is roughly 44 percent lower than the national average and serious attacks are rare.

According to Below Deck Nantucket, the island recorded roughly 165 reported crimes in a recent year, including about 30 violent offenses and 135 property crimes.

Police records indicate the previous reported stabbing on Nantucket occurred in July 2019, while the one before that was in June 2012.

According to the police report, the injured man suffered an approximately 2.5-inch laceration to his left forearm and a 1.5-inch wound to his upper left chest or rib area before being airlifted by MedFlight from Nantucket Cottage Hospital to a mainland hospital for specialist treatment.

Investigators say the injuries will require multiple surgeries.  

Officers arrived to find the wounded man on the ground while a passerby pointed them toward Downer, who was sitting on a nearby sidewalk waiting for police.

The altercation unfolded in the heart of the island's bustling downtown, behind The Juice Bar and The Rose & Crown, prompting Nantucket Police, Massachusetts State Police and EMTs to flood the area as officers sealed off the street with crime scene tape.

Witnesses told investigators the confrontation involved Downer, who was making deliveries in a Sayle's Seafood truck, and the driver of a Myles Reis garbage truck.

According to the police report, the injured man later told officers he shouted a Jamaican profanity at Downer before the confrontation escalated.

He claimed he saw Downer pull what police described as a three-inch pocketknife from his waistband and only realized after the fight that he had been stabbed in both his forearm and chest.

Downer gave detectives a sharply different account.

According to the police report seen by the Nantucket Current, he said he and the other man came from the same parish in Jamaica and that he had heard the man 'had issues with him.'

Downer told police he was unloading juice deliveries when he was suddenly punched in the back of the head.

'Downer stated he turned around to see who it was and was then kicked in the chest. Downer stated that he then pulled a pocketknife from his pocket and swung it towards the alleged victim approximately two to three times,' the police report states.

Defense attorney Rob Moriarty argued those facts amount to a straightforward case of self-defense.

'He has housing, he has no prior criminal record,' Moriarty told the court. 'Mr. Downer defended himself. This is straight self-defense.

'The other individual is bigger than him. Mr. Downer is relatively small in stature. The other individual is much larger and surprised him.

'Apparently, this had something to do with a girl that led to this individual attacking him. He was attacked without warning, was surprised, and defended himself.'

Moriarty said surveillance footage he reviewed fully supports Downer's version of events and shows his client was attacked first while making deliveries.

The attorney also criticized Nantucket Police for keeping Downer in custody overnight instead of bringing him before a judge on Tuesday afternoon.

'He should have been brought for an arraignment at 3 o'clock (Tuesday afternoon) at the latest. It's unconscionable,' Moriarty argued.

Investigators also allege Downer entered The Juice Bar after the stabbing looking for another knife.

According to the police report, Downer told officers he went inside searching for a knife in case the alleged victim returned.

A witness, however, told police Downer grabbed a chef's knife measuring between 10 and 12 inches before another employee intervened and took it away.

Downer remained at the scene until officers arrived and arrested him in handcuffs.

Moriarty has filed a motion seeking dismissal of the charges. 

Prosecutors requested additional time to respond to the motion, and a pretrial hearing has been scheduled for June 30.