A teenager accused of murdering an older boy in a knife attack told a jury how he "just flipped and saw red" before the stabbing.
The 17-year-old, who was 16 at the time, claimed he wanted to flee when he saw Michael "Angel" Graham on Scarborough sea front but was "frozen to the spot".
He told Teesside Crown Court he could not remember removing from his pocket the flick-knife a friend had bought for him earlier that afternoon
He maintained he thought he was only punching 19-year-old Mr Graham in the back - when he was actually stabbing him, the murder trial was told.,
The jury has been told Mr Graham, 19, from Scarborough and Leeds, died after being stabbed 12 times in the back in a brawl on Scarborough seafront.
Mr Graham's 17-year-old friend was also wounded in the leg when he went to help his pal, the jury has heard.
The trial has been told Mr Graham's attacker counted the knife thrusts so he could later text friends he had stabbed Angel 12 times.
Victim and killer had been friends but fell out after Mr Graham taunted the younger boy for sleeping with a 12-year-old girl, it has been alleged.
Yesterday the accused murderer described how he and seven other teenagers made their way down to Foreshore Road from McDonald's via the Italian Gardens on the night of the double stabbing.
They were walking down the path two at a time and were at the bottom when the spotted Mr Graham and his 17-year-old friend.
The defendant told the jury: "I froze my steps. My scared face came on.
"I did not want to move or take any further steps towards the beach.
"I was scared and my face went white. I was scared and worried what would happen next."
As he got down to the bottom of the steps through the gardens - with the knife in the right hand pocket of his jacket - he saw one of his friends and Mr Graham punching each other.
Mr Graham was sat on top of the other man with his knees pushed up against his opponents armpits, it was said.
Mr Graham was trying to move up to pin the other man's shoulders down, the accused man continued.
The defendant and the rest of the group were gathered in a semi-circle about five or six feet away watching Angel beating the other man up, the court heard.
"I thought it was going to be me next," the defendant said.
"I was scared and worried. I wanted to leave but was frozen to the spot and couldn't.
"I just could not move. I was watching him being beaten up and thought I can't leave him here while that's happening."
He said all the text insults that he and Michael Graham had been trading were going through his head along with all the older boy's name-calling and "bullying".
He went on: "I was angry, frustrated, ready to blow and ready to flip.
"I just flipped and saw red. I could not control myself. I came up from behind. I thought I was just hitting him in the back."
Paul Greaney QC, defending, asked: "Were you just hitting him in the back?"
His client replied: "No I was not. I was stabbing Angel in the back."
He said he could not remember taking the knife from his pocket.
"I just remember flipping and going for him. I just thought this was it," he continued, adding he thought it was him that was going to be stabbed.
Tim Roberts QC, prosecuting, , said the knife had been purchased at 5.15pm that day by an older boy - using his ID- because the defendant was too young to purchase it legally.
He stabbed so hard he cut his own hand, the prosecutor said, adding that his victim had been "defenceless" and did not even know his attacker was behind him.
Angel - who had been living in Scarborough but had links to Chapeltown, Leeds - died from multiple wounds to his back shortly after the incident on April 13.
The accused, who is now 17 but cannot be named for legal reasons , denies murder.
An order has also been made banning identification of anyone else involved in the case - because of their ages - apart from the dead man.
The trial continues.