PORT HAWKESBURY, N.S. -- The captain of a Cape Breton lobster boat who pleaded guilty to manslaughter for his role in a violent death at sea should receive a much lighter sentence than one of his co-accused because of his fragile mental state at the time, his lawyer told a sentencing hearing Monday.

Lawyer Nash Brogan said Dwayne Matthew Samson of D'Escousse, N.S., should be sentenced to between six and eight years in prison because he has openly admitted he was steering the Twin Maggies on June 1, 2013, when it struck Phillip Boudreau's boat off Petit-de-Grat, tossing him into the water.

Boudreau's damaged, overturned skiff was found shortly after he disappeared. The 43-year-old's body has yet to be found.

An agreed statement of facts, read into the court record Monday, says Samson and one of his deckhands, Joseph James Landry of Little Anse, believed Boudreau was tampering with the lobster traps they were hauling up that morning at 5 a.m. at the southern tip of Cape Breton.

The statement, presented in Nova Scotia Supreme Court in Port Hawkesbury, says that soon after the three-man crew spotted Boudreau's four-metre boat, Samson asked another deckhand to load a rifle, which was then handed to Landry.

Landry, who is Samson's father-in-law, used a rifle to shoot at Boudreau's boat four times, hitting him once in the leg, the document says. When Landry fired the second shot, Boudreau tried to get away but his propeller got tangled in rope, causing his boat to sit idle.

The statement says Landry then told Samson to turn the Twin Maggies around so he could tie a rope to Boudreau's boat and tow it out to sea.

With Samson at the wheel, the Twin Maggies rammed Boudreau's boat three times, knocking him into the water. The document says Landry hooked Boudreau with a gaff and Samson sailed the Twin Maggies out to sea, where Boudreau's body was dumped in about 20 metres of water.

Landry was sentenced earlier this year to a 14-year prison term after a jury found him guilty of manslaughter in Boudreau's death, although he is appealing his sentence.

The other deckhand, Craig Landry, was sentenced to 28 days in jail for being an accessory after the fact.

In his closing submission, Crown attorney Shane Russell said Samson should be sentenced to 12 years in prison. He said Samson was an active participant in a crime that could not have happened without his help.

Russell said it was Samson who called for the rifle to be loaded, and it was Samson who steered the Twin Maggies into Boudreau's boat and later out to sea.

"He was not an innocent bystander," Russell told the court, adding that Samson used multiple weapons, including his boat. "He was not merely the driver of the getaway boat."

Earlier in the day, Brogan presented a psychiatric assessment to the court that concluded Samson had suffered a panic attack shortly after the first shot was fired.

The report, prepared by forensic psychiatrist Scott Theriault more than two years after Boudreau's death, quotes Samson as saying he "was in a state of panic" and "saw red" at the time of the shooting.

Theriault's report goes on to quote Samson saying he felt "like I was above and looking down" at the violent scene unfolding around the two boats. Samson also said there was "no time to think," amid a "whirlwind of events" that left his heart pounding, his mouth dry and his clothes soaked with sweat.

The Halifax-based psychiatrist told the hearing the symptoms were consistent with a typical panic attack and a disassociative disorder.

When Crown attorney Steve Drake asked Theriault if someone could find a list of those symptoms by using Google, Theriault said that was possible but he said Samson did not appear to be psychologically sophisticated, which meant his recollections came across as genuine.

Theriault agreed, however, that there was no way for him to discern whether Samson was telling the truth about what he experienced that day. As well, he said the panic attack may not have rendered him incapable of making decisions or steering the boat.

Brogan told the court that James Landry was the "principal player" in the case, which is why he received such a stiff sentence.

Outside court, Brogan said his client's mental condition was such that he could do little else but obey the commands of James Landry.

"They started off being angry and it developed into a state of high panic where they couldn't resist the commands of James Landry," Brogan said.