Macdonald, 32, has denied murdering Mr Guy, 31, in the driveway of his Feilding home early on July 8, 2010.
The Crown alleges Macdonald shot and killed Mr Guy after growing tensions over the future of the family farm they co-managed.
The second half of a police video interview with Macdonald is being shown to the jury at the High Court at Wellington today.
The more than four hour-long interview was conducted at the Palmerston North police station last April 7 - the day Macdonald was arrested and charged with murder.
In the interview, Macdonald admitted to burning down an old house on the Guys' property, vandalising a new house being built there and stealing two deer from a neighbouring farm.
But after more than three hours of questioning he denied murdering Mr Guy, saying he had "nothing to explain".
"I have nothing to do with that," Macdonald said.
"It looks obvious, these leading-up-to events, but I'm not that psycho."
Macdonald said he could "see the finger points at me" but maintained he did not do it.
Mr Howell said he did not have an alibi, knew the area well and had the motive of control of the farm.
Macdonald replied: "Personally I don't think that would have achieved anything for me."
He said it had been a "total pain in the ass" without Mr Guy on the farm.
Macdonald was arrested after denying the murder but confessing to the other acts.
Earlier in the interview, Mr Howell asked Macdonald whether he had vandalised a new house being built on the Guys' property.
The Crown alleges he damaged the house, and earlier burned down an old house on the property, to intimidate Mr Guy's wife Kylee off the farm.
Mr Howell said he was "pretty concerned" by inconsistencies in Macdonald's statement and asked him bluntly: "Did you go and do that damage to the house?"
Macdonald said he did not and denied any knowledge of the damage.
Mr Howell said police had formed the view that whoever committed the attacks was responsible for Mr Guy's murder.
"I guess it sort of makes sense," Macdonald replied.
Mr Howell later asked Macdonald if he thought his friend and workmate Callum Boe had told police the truth about the damage.
Macdonald replied he thought he had.
Mr Howell then asked him if he wanted to change his story based on what Boe - his younger accomplice - had told police.
"He was probably involved," Macdonald said.
Asked who with, Macdonald said: "Me."
Macdonald said Kylee had not done anything to him but agreed it was directed at the Guys.
"I don't know if it was about the new house ... It wasn't a fair partnership. Slogged my guts out, worked my ass off."
Asked about his earlier comments that he had got over his disagreements with Mr Guy, he said: "I still was holding a bit of a grudge."
Mr Howell also asked him about the arson of the old house on the Guys' property.
Macdonald said he "burnt it".
Asked why, he said: "I don't know. Yeah, just thought that it would be funny ... It wasn't directed at Scott and Kylee in vengeance."
Mr Howell also asked Macdonald about his involvement in the theft of two deer from the nearby Hocken farm.
"We took two deer. I don't have to explain more than that."
Mr Howell asked him why.
"I don't know, it was a challenge. I don't have a reason why, we just did it."
Macdonald admitted he buried the deer on the farm by a rubbish hole on the same morning he and Boe took them.
He denied any knowledge of notes left in the Guys' letterbox.
The video screening continues.
