HAMILTON -- Dellen Millard fatally shot Tim Bosma and later disposed of his body in an animal incinerator dubbed "The Eliminator," his co-accused told their murder trial as the victim's family and friends wept in the courtroom.

"He looked mad, like a lunatic, like something came over him," Mark Smich said of Millard as he got out of Bosma's truck during a test drive three years ago.

Smich took the stand Wednesday in his own defence and related his version of the events that occurred the night the Hamilton man was killed.

Bosma's widow sobbed and his mother rushed out of the courtroom, tears streaming down her face.

Smich said he saw Bosma's body slumped over the dash of his Dodge Ram truck and a bullet hole through the window shortly after going on a test drive on the night of May 6, 2013.

"There was a lot of blood," Smich told the jury.

Smich, 28, of Oakville, Ont., and Millard, 30, of Toronto, have pleaded not guilty to first-degree murder in the death of Bosma, who vanished after taking two strangers on a test drive of a pickup he was trying to sell.

Smich testified he and Millard had planned to steal a truck and were going on test drives to "scope out" vehicles, adding that he helped research the trucks on the Kijiji and Autotrader websites with Millard setting up test drives with a pre-paid phone.

The idea was to return later to steal a truck if the conditions were right, Smich told the jury, but said there was never a plan to bring a gun or hurt anyone.

Smich said Millard was driving and Bosma was the passenger in Bosma's truck and he was following in Millard's Yukon, when the Dodge suddenly swerved to the side of the road "some time" into the test drive.

Millard, Smich said, got out of Bosma's truck, came over to Smich and said he was "taking the truck" and grabbed a flashlight from the Yukon.

"I got out and I see a bullet hole through the window and Mr. Bosma laying head first on the dashboard," Smich said.

"I was shocked. Utter and complete shock. I was in disbelief," Smich told court about seeing Bosma's body in the truck.

"I said 'what the f--k is going on?' Dell (Millard) looked liked something came over him ... I never seen him like this," Smich said.

Smich said he freaked out, but was terrified of Millard, who told him to change license plates between the two trucks.

"At that point, I didn't know, I felt like I had no choice. I was scared," Smich said.

Smich also said he thought he saw Millard put a gun into a satchel he had draped over his shoulder as he got out of Bosma's truck.

"I did not know he bought a gun," said Smich, who had earlier described Millard as "kinda like a bigger brother."

He said Millard got back into Bosma's truck and he followed as they drove to Millard's farm near Waterloo, Ont.

At that point, Smich said he got a better look at Bosma's body.

"There was blood all over the whole left side of Mr. Bosma, all around his head," Smich said.

Smich said Millard then wrapped Bosma's body in a sheet and told him to put it into the incinerator, but Smich said he couldn't because he had injured his shoulder.

Millard dumped the body into the incinerator, but was "in a huff" about having to do it himself, Smich testified.

The pair hooked up "The Eliminator," which was on a trailer, to Bosma's truck and Millard drove it to his hangar at the Waterloo airport with Smich again following in his friend's truck, Smich said.

At the hangar, Smich said, Millard turned on the incinerator with Bosma's body inside.

He said Millard told him to strip Bosma's truck, which he said he did by cutting out the carpet and seat belts and washing out the blood with a hose. They worked together to remove all the seats.

He told court he didn't go to police because he was scared and confused and wanted to speak to a lawyer.

Later in the week, Smich said he helped Millard and one of his workers continue to strip the truck, which Millard wanted to paint red.

"This time when I seen him, he was back to normal Dell (Millard), just normal Dell," Smich said. "He was absolutely normal Dell, which scared the s--t out of me even more."

He said after Millard's arrest, he asked one of their mutual friends to get drugs out of Millard's home in Toronto. Along with the bag of drugs, he said he received a toolbox that had a gun inside, wrapped in cloth.

The gun, a Walther PPK, was the same gun he saw Millard put in the satchel the night Bosma died, Smich said.

"I didn't kill Mr. Bosma," Smich said.