A former soldier accused of murder sobbed as he told a jury he felt "disgusted" when looking back on what he did to his victim and his family.
Karl Pascoe said he was "defending himself" when he attacked Joseph Leech with a fence post in the early hours of December 23, 2013.
Mr Leech survived his injuries, but Newcastle Crown Court heard he was "never the same again".
The 32-year-old, who became prone to having fits, went to bed at his parents' home for an afternoon nap on April 2 last year and "never woke up".
His lifeless body was found by his mother.
The court heard how Pascoe was discharged from the army when he was convicted of assault in the aftermath of the attack.
The 31-year-old, of Blackfell, Washington, is now accused of murder.
He denies the charge and is being tried by a jury.
Pascoe, who was a guardsman for the Coldstream Guards, was on pre deployment leave at the time of the incident.
He told the court he was due to be deployed to Afghanistan in February 2014 and was visiting his cousins and friends in Washington.
During his evidence, Pascoe told the jury how he saw Mr Leech walking down the opposite side of the street with a piece of wood and crossed the road to "try and calm him down."
He said: "I said something along the lines of 'who ever it is, it's not worth it'.
"I was trying to calm him down from doing anything he might regret doing."
When asked by Richard Wright QC what he thought was going to happen, Pascoe replied: "That he was out looking for trouble because he had a piece of wood in his hand.
"He wasn't happy.
"He told me it had nothing to do with me.
"He went to strike me with the piece of wood."
Pascoe told the jury how he took the piece of wood from Mr Leech and used two hands to hit him with it.
He said: "I thought he was going to go for me."
When asked why he hit Mr Leech a second time with the piece of wood, Pascoe said: "I thought he was going to come back at me.
"I wasn't thinking about how much force I used at the time."
He told the court how he hit Mr Leech, who was on his knees, a third time to his head with the piece of wood as he was trying to get back up.
Pascoe said: "He was down on the floor. Lying on his front."
When asked what he thought he had done to him, Pascoe replied: "Killed him".
He said that was not what he wanted to do.
When Mr Wright asked why he had done it to him, Pascoe said: "Because I thought he was going to hurt me."
Pascoe said he was "disgusted" when asked how he felt about what he had done to Joseph Leech and his family.
He said looking back he should have carried on walking and not crossed the road.
The court previously heard how Pascoe caused severe damage to Mr Leech's skull and brain when he attacked him.
Nicholas Lumley QC, prosecuting, asked Lumley why he did what he did, to which Pascoe replied: "I would have said I was defending myself."
Pascoe denies murder.
The trial continues.