HALIFAX -- A witness testified Monday that he was becoming intimate with Montreal-born yoga instructor Kristin Johnston when Nicholas Butcher unexpectedly came into the bedroom, hours before he allegedly killed her.

Michael Belyea told a Nova Scotia Supreme Court jury that Butcher found Johnston in Belyea's flat in the early hours of March 26, 2016.

She broke up with Butcher, but he later returned to find her kissing Belyea in his bedroom -- who, despite the drama, said he was never concerned for Johnston's safety.

"He didn't seem aggressive with her, even verbally aggressive. He was not happy about the situation, but there was nothing that would lead me to worry about her physical safety," he testified.

Butcher is on trial for the second-degree murder of Johnston, who was found dead later that day in her Halifax-area home.

Belyea said that Johnston, 32, had come to his flat with her friend Lisa Abramowicz, where the 41-year-old carpenter and musician said the three were listening to a Johnny Cash record and sharing a drink.

He testified that he heard footsteps coming up the stairs to his upper-level flat in a two-unit house.

Belyea said it was a man in his 30s he'd never seen before, and assumed the person was looking for someone in the lower unit. He said eventually the man said he was looking for "Kristin."

"He was being very quiet and looking around a bit and I found it difficult to get an answer out of him," said Belyea. "I definitely found it strange that he was being so quiet."

Belyea said he led the man around the corner to where Johnston was, and said she appeared shocked to see Butcher, asking him how he had found her.

Butcher and Johnston talked in the kitchen and then at the bottom of the stairs before Johnston came back alone, and said she had broken up with Butcher, said Belyea.

Several friends and family have testified that Johnston was not happy in the relationship and wanted to break it off.

Belyea said Johnston then said she was tired and was going to sleep over, and went into the bedroom. He said goodbye to Abramowicz and followed Johnston. He closed the door behind him, and heard Abramowicz leave soon after.

Belyea -- who said he had previously been intimate with Johnston when they first met in 2009 -- said he laid on the bed with Johnston and they started kissing.

Then, he heard footsteps coming from the kitchen. He assumed Abramowicz had forgotten something, but then he felt a push on his shoulder.

It was Butcher.

"He said to her something like 'What are you doing' or 'Why are you doing this'," said Belyea, as the 35-year-old accused looked on emotionless from his lawyer's bench.

"I remember her saying, 'This is where I want to be'."

Belyea said he asked Butcher what he should do, and he asked Belyea to give them some space. He said he went into the kitchen, but then thought his continued presence at the flat might make things worse, so he decided to step outside for a walk.

Belyea was gone for about 15 minutes, and when he returned, Johnston and Butcher were gone.

She sent him a message apologizing for what happened at 5:30 a.m.

Hours later, Johnston was found dead.

The Crown alleges that Butcher killed Johnston and tried to kill himself at her home in Purcells Cove.

Prosecutor Tanya Carter has said the medical examiner will testify that Johnston had 10 wounds on her neck, and that her death was caused by sharp force.

Butcher has pleaded not guilty.

Earlier Monday, defence lawyer Peter Planetta appeared to question the reliability of Abramowicz's memory of the evening.

Abramowicz testified that the last message she sent to her childhood friend was, "How's" -- short for how's it going -- as she wanted to check in with Johnston after leaving her at Belyea's flat.

However, Planetta noted the message also included several kiss-face emojis, and that Abramowicz had not mentioned those in her previous testimony. He asked if the emojis had to do with Belyea, and she said no.

Abramowicz, 34, said she had also sent Butcher one message that same morning, but Planetta pointed out she had actually sent him two messages.

He suggested that if she couldn't recall certain details about the messages she had sent two years ago, perhaps her other memories were not complete.

"Certain things from that night stick out very clearly to me," Abramowicz replied.

She also testified that weeks before the alleged murder, she had a phone conversation with an inconsolable Butcher, in which "he bawled like a baby for about an hour and a half."

Planetta pointed out that this was new information, and that she had made a police statement, testified at an earlier court hearing and met with Crown prosecutors in relation to the case.

"You had every opportunity to say everything that was on your mind and you didn't mention at any time this 90-minute conversation with Mr. Butcher," he said.

Abramowicz replied: "If I didn't mention it, it's because I wasn't asked about it."

Planetta then suggested that she didn't tell police about the conversation, but brought it up Monday, because she's "willing to do whatever it takes to make Mr. Butcher look bad."

"No, I'm saying exactly what happened," she said, at times becoming visibly frustrated with Planetta and making comments that prompted a few cautions from Justice Joshua Arnold.

The trial continues Tuesday with the cross-examination of Belyea.