On August 18, Regts said, a fellow camper came to his site and asked for help.
"The lady from the campsite next door said there'd been a boating accident, a drowning, and asked if I could come down to help," Regts said.
"We found a pontoon boat beached. There were two people and the decedent on board."
The court has previously heard Beckett and his wife were out on a Zodiac dinghy when Letts-Beckett went overboard. Beckett told police he attempted to save her, but struggled to get far enough underwater to pull her to the surface.
He said he was eventually able to drag her to shore. After unsuccessfully attempting to revive his wife, he said, he went out in his Zodiac to seek help from the couple in a nearby pontoon boat.
Jurors have been told the pontoon boat brought Letts-Beckett back to the campground. When Regts arrived at the beach, he said Beckett was sitting at the back of the pontoon boat looking at his wife's body.
"I got a story as to what happened," Regts said.
"I assessed the patient to see whether she was viable. She was not."
Regts said Letts-Beckett was unconscious, not breathing and had no pulse.
He said Beckett was upset after being told his wife could not be resuscitated, but then asked a strange question.
"He asked me if there was going to be bruises on his wife," Regts said. "I was a little taken aback. I said there might be bruises on her back where she was dragged across the rock [after being pulled to shore]."
Regts said he noticed no bruising on Letts-Beckett's body, but said he followed protocol as a precaution. "We used BCAS (BC Ambulance Service) guidelines and treated it as a potential crime scene," he said. "We made sure nobody touched the body."
Pathologist Yann Brierly performed Letts-Beckett's autopsy in Vernon two days after she died.
In court, he said the cause of death was drowning, but noted an area of redness near Letts-Beckett's left cheekbone.
"Pre-mortum injury can't be ruled out," he said. "But there are a lot of cases where we get unexplained red areas on bodies."
Brierly also said he found no evidence - chest injuries - of CPR having been performed on Letts-Beckett's body. Beckett told police he performed CPR on her after pulling her from the water. Another witness also said he helped with chest compressions.
Brierly said chest injuries, including fractured ribs and red skin, are common when CPR is done "with appropriate vigour".
Beckett and Letts-Beckett met in 1995 in New Zealand. Five years later, he moved to Westlock, Alberta, to be closer to her. The couple married in 2003. Previous witnesses have described their relationship as a rocky one. The Becketts split briefly in late 2007, but reconciled months later. Letts-Beckett also went to police alleging physical abuse on the part of her husband, but no charges were laid.
The trial, which began in mid-January, is expected to last three months.