Landry had been charged with second-degree murder, but the jury found him guilty of manslaughter.
CBC News has obtained the police video of Landry's confession. It was recorded by RCMP in June 2013, one day after Landry was arrested and one week after Boudreau disappeared.
The video was shown in court as part of the Crown's case against Landry.
Landry is questioned by RCMP officers for more than four hours. At first he denies killing Boudreau, but later admits to it over the rage he felt when he saw Boudreau cutting lobster traps and taunting him.
"I was seeing black. I was so mad," Landry says in the video.
In the video, Landry tells the investigator he took a Winchester .30-30 and shot four times at Boudreau, then ran over the man's smaller boat with the Twin Maggies, the lobster boat he worked on.
"So when you fired those first two shots at Philip, what was your intention?" the investigator asks.
"Killing him," Landry replies.
"Killing him?" the investigator repeats.
"I'm telling you the truth. It's no good — he was no good. You told me not to lie, so I'm telling you the truth," says Landry.
"That's all I want from you," the investigator responds.
"Well, there you go. It's all over now," Landry says.
A jury delivered the manslaughter verdict late Saturday afternoon.
Landry is scheduled to be sentenced on Jan. 29. He remains in custody.
Dwayne Matthew Samson, the captain of the Twin Maggies, is also charged with second-degree murder.
Samson's wife, Carla, owner of the lobster boat and Landry's daughter, faces a charge of accessory after the fact.
Craig Landry, a third cousin of James Landry, is charged with accessory after the fact.