David Bain was "shocked to the core" to hear his groomsman had committed a second murder.

Paul Wilson, 55, also known as Paul Tainui, has pleaded guilty to raping and murdering Christchurch 27-year-old Nicole Tuxford in Merivale last year.

He raped and murdered 21-year-old West Coast woman, Kimberly Schroder, in 1994.

Wilson met Bain in jail and was groomsman at Bain's 2014 wedding.

Joe Karam, long-time advocate for Bain, says Bain is distressed Wilson inflicted such terrible disaster on the victim and her family.

He says Bain thought his friend was managing life well and there was no indication he wasn't.

READ MORE: David Bain's groomsman named as Christchurch murderer

Wilson lay in wait for eight hours overnight, before 27-year-old Nicole Marie Tuxford arrived back in her Merivale home – in April last year.

Wilson has pleaded guilty to sexual violation in the High Court in Christchurch this morning.

On talkback this afternoon, people shared their experiences with criminals – including one who knew Paul Wilson in

Caller Lyall met Wilson while on a tour of Papamoa Prison. He had dinner with him as part of the tour, and that Wilson surprised him.

“I couldn’t help himself and I asked him ‘what did you do’? He said ‘I won’t tell you that, but what I will say is that if this was France, I wouldn’t be here, as it was a crime of passion, I would have got off.”

Lyall says that Wilson seemed like a nice guy, but when he got home, he Googled and was blown away by how horrific the crime was.

“It reaffirmed my view that those people should never go to prison, they should go straight to the gallows.”

Caller Susan added her take, with her experience of befriending a gentleman who raped her daughter.

She said that at face value, he seemed like a really nice guy.

“The thing is that he also offered to be the person where my children could go when I had a protection order, the person who was going to oversee that they were okay.”

She says that she regularly appealed the parole as she did not feel he had been rehabilitated.