Horror unfolded at a Cape Cod restaurant on Saturday night when a masked man shot a beloved father in the face as diners watched on, according to police.  

Nicholos Campbell, 26, is accused of killing Careeme Harakh, 35, inside the Moonfish Restaurant & Tavern in Dennis, close to the shore by Nantucket Sound.

Police said Campbell opened fire on Harakh at the eatery just before midnight on Saturday, and officers detained him in nearby Barnstable at 12.05am. 

He pleaded not guilty to one count of murder at Orleans District Court on Monday. 

Campbell's lawyer claimed his client was attacked first, describing the shooting as a 'classic case of self-defense,' while prosecutors said witnesses disagreed. 

Prosecutors said Harakh was shot at short range after an altercation at the restaurant, as traumatized diners including the victim's father watched on. 

Assistant District Attorney Alexandra Isaacs said Campbell was wearing 'a balaclava or ski mask' which covered his head, neck, and face at the time of the shooting. 

Harakh's father, Clinton, said he 'heard gunshots and ducked for cover' and later realized his son had been shot, according to Massachusetts State Police. 

Officers rushed to the scene and found Harakh lying in the main dining room with a large pool of blood surrounding his head.  

Clinton told investigators he saw a man running away but did not know who he was. 

Campbell fled the scene but later called 911, telling a dispatcher he 'had to shoot someone to defend himself because he was jumped and stabbed in the head.'

He turned himself in to the police station in Barnstable, where he lives, telling police: 'I did something bad,' prosecutors said. 

Campbell claimed he was attacked by two men who repeatedly punched him in the head, and he believed one of them may have been armed.

He said he began losing consciousness, and shot three times in a panic. 

Isaacs said police searched Harakh and found only his cellphone and keys in his pockets, and that the victim had gun residue on his face, suggesting he was shot at close range. 

She added that several witnesses also said nobody saw 'this alleged altercation beforehand' in which Campbell 'claimed he was attacked.'

Campbell's lawyer, Emir Sehic, said his client was 'talking next to somebody else when he was approached by the decedent, the primary aggressor in this situation.'

Sehic said Campbell was left with a metal staple in his head and bruises as a result of the alleged attack.

He described Campbell as 'a law-abiding, good person in a horrible situation who had to do something bad.'

Harakh's sister, Jascha, said in an interview that her family was furious over Campbell's claim that he acted in self-defense. 

'He came there to murder Careeme,' she told the Boston Globe. 'Cold-blooded.' 

'The person that was in court murdered my brother,' she said. 

'I feel like we need justice for that. He cannot make us laugh anymore. He cannot cook for us anymore. He cannot tend to his daughter anymore.' 

A fundraising page launched by Jascha described her brother as 'a devoted father' who leaves behind his wife and their eight-year-old daughter, Allison. 

'His sudden loss has left Allison and her mother facing unimaginable emotional and financial challenges,' the GoFundMe reads. 

'Allison's mother is now struggling to provide for her daughter while coping with the grief of losing her partner.'