HAMILTON -- The former girlfriend of a man facing murder charges in the death of Tim Bosma testified on Thursday that her boyfriend told her it was his friend -- and co-accused -- who shot and killed the Hamilton man.

Marlena Meneses, one of the Crown's star witnesses, told court her boyfriend, Mark Smich, and his friend, Dellen Millard, picked her up the morning after Bosma disappeared nearly three years ago.

"They were just really happy, saying they wanted to celebrate," Meneses told court.

Bosma vanished on May 6, 2013 after taking two strangers for a test drive of the truck he was trying to sell. The Crown alleges Bosma was shot at point-blank range inside his truck and later his body was burned in an animal incinerator.

Smich, 28, of Oakville, Ont., and 30-year-old Millard, from Toronto, have pleaded not guilty to first-degree murder in Bosma's death.

Meneses, 22, said she was watching television with Smich, whom she had been dating for about a year, when Millard's name popped up on the screen. The newscast said he'd been arrested in connection with Bosma's disappearance.

She told jurors she "freaked out" and asked Smich about Bosma.

"He told me that Mr. Bosma was gone, gone," said an emotional Meneses. "He just said that Dell (Millard) murdered him."

"Did he say how?" asked Crown attorney Craig Fraser.

"That he shot him," she said.

Bosma's widow, Sharlene, broke down in tears in court, as did many other family members. Smich looked straight ahead while Millard stared at his co-accused, looking at him up and down.

Fraser asked if she knew what happened to Bosma.

"I believe (Smich) told me that they burned him."

When asked why she didn't go to police, Meneses said she "should have -- I was stupid."

"Did you ever ask Mr. Smich why Mr. Bosma was shot and killed?" Fraser asked.

"No," she said. "I didn't want to know. I didn't want to know anything."

Meneses said she continued to plead with Smich to go to police in the days that followed.

"I said he had to come clean, go to the police because there is a family out there with a missing father and that's not fair and you need to go and give this family the proper closure," she said.

The Crown also asked about a gun they allege was hidden inside a toolbox that Smich picked up after Millard had been arrested.

"He told me that he wrapped it in duct tape and buried it somewhere," she said. "Somewhere in a forest."

Court has previously heard that police found the shell casing from a bullet in Bosma's truck, along with gunshot residue. Gunshot residue was also found in the toolbox, which police located after Smich was arrested on May 22, 2013. But the toolbox was empty.

Meneses also told court that she overheard Smich and Millard talking about stealing a truck in the days before Bosma disappeared.

She said she tried to discourage her boyfriend from going through with the theft.

"I said some things to try to change his mind," Meneses said. "But he didn't listen to me."

Smich and Millard were close, she said, like brothers.

"Mark cared for Dellen more than any other person," she said. "He was in love with him."

Meneses said she was really worried about their plan to steal a truck. She said she spoke to Smich on the phone around 9 p.m. on May 6, 2013, which is the same time court heard that Bosma left his house in rural Hamilton with two men.

Smich told her he couldn't talk because he was driving. Meneses said she found that unusual because Smich didn't have a driving license.

"I was very scared," she said. "I knew that they were going to go steal a truck. I didn't know if he got hurt or what was going on."

Meneses said Smich and Millard picked her up around 8 a.m. the next morning, and they were both "very happy" because "the mission went well."

Meneses later described being arrested alongside Smich on May 22, 2013, saying Smich was "emotional, yelling and screaming, telling me not to say anything" about what he'd told her about Bosma.