The former girlfriend of a man charged with murder says his dislike of the victim "didn't stop", right up until the day he was shot dead.

Macy Randall had been in a relationship with Adrian Phillips for about four years when he shot Bayden Williams dead on the side of the winding Kopu-Hikuai Rd near Thames.

She recalled the moment Phillips told her what happened after she went to pick him up shortly afterward.

"He got out of his ute and walked up to my window and he told her that he f***** up, he thinks that he hurt Bayden ... he thinks he killed him.

"He told me that he ran him off the road and shot him."

As they drove back to his parent's house, she called his sister for advice, and then called 111.

Asked by Crown prosecutor Jacinda Hamilton how he seemed at that point, Randall said "very confused".

"Like he wasn't sure what was going on. He was very, very upset ... he was crying."

As for how she felt, she was also confused.

"I wanted him to tell me it wasn't real. I begged him. I never thought he was capable of something like that. I was scared."

Randall, 22, and her twin sister Chloe were in relationships with Phillips and Williams respectively. They were friends, she said and hung out a lot.

She said he started to change after he was seriously burnt after he poured alcohol on a bonfire in the driveway of their new rental in December 2018.

Bayden Williams was shot dead on the side of the Kopu-Hikuai Rd in August 2020.

He spent three weeks in hospital recovering from his injuries and made good physical progress so decided to return to work as a mechanic at Nissan Paeroa.

However, Randall said he was only meant to ease back into work due to his skin grafts by doing about an hour a day.

That never eventuated and he was made to work full days from the beginning, which annoyed Phillips.

"The way they were treating him. It was pretty unfair. He would get quite upset about it.

"He felt used and taken advantage of. I was upset because he was a real asset to the team."

That frustration shifted into their personal life and he would get angry and "lose his temper a lot".

"He was going through a lot of ups and downs. It was very emotional."

He would ultimately quit his job and move out of the rental they shared together and back to his parents' place.

She then set about supporting both of them on her wage from Pak n Save Thames.

After an incident involving her father, Peter, and Williams' father, Lance, Phillips no longer liked Bayden.

"He felt like we were let down and nothing was done about the incident ... he would get quite wound up about it, upset and angry.

Asked by Hamilton how long the "anger and upset" lasted towards Williams, Randell replied, "it didn't stop".

In the lead-up to the shooting, there were also several incidents with her that left her scared, usually while driving.

Once was when they were driving back from Miranda, and despite repeated requests to slow down or stop, he would ignore her.

"He thought that I was just trying to stress him out, so he started yelling ... I was really scared ... he started driving quite recklessly and was smashing the steering wheel."

When she told him she'd call the police, he told "he'd run us off the road".

She recalled another time when he was driving dangerously; speeding around corners and stopping to do skids.

As she'd been in a car crash before, she asked him to slow down. He wouldn't.

Randall also remembered going for a drive on August 2, just three days before the shooting, so that he could ease her concerns about the new shotgun he'd bought.

She told the court she was more worried about him using the gun on himself.

"I was anxious about it ... he would try and make me feel better about it, telling me that it would be locked in the back seat of his ute all the time and he'd teach me about gun safety."

Asked about a Facebook post by her sister, Chloe, on August 3 stating that a visit with
Williams and their son went well, Randall said they ended up having an argument about her getting back together with him.

It saw her move out and back in with Phillips at his parents' house in Ngatea.

- Belinda Feek, Open Justice