EDMONTON – Alberta RCMP say three girls endured years of horrific sexual abuse and psychological imprisonment, allegedly at the hands of their father, before he was arrested and charged with 23 offences.The 41-year-old man, whose name is under a publication ban, was arrested in a small town west of Edmonton last November after an investigation by a coalition of Alberta law enforcement agencies known as ALERT.Staff Sgt. Stephen Camp said Friday that the man allegedly sexually abused his daughters multiple times over the last six years when they were under the age of 18. He declined to give their ages.He said one of the alleged victims was procured for sex on multiple occasions to strangers through online ads and the father video- recorded the assaults.“It is quite nauseating,” Camp said. “It makes the investigative community feel actually quite sick to think that for so many years of their childhood, they were psychologically imprisoned by their father for a sick and sexual purpose.“These crimes are quite monstrous to the family and to society at large.”On the day of their father’s arrest, “it was as if a dark cloud had been taken away and lifted from their lives,” Camp said.The girls, who lived with both parents and two brothers, were home-schooled and isolated from society, Camp said. Their mother was a victim as well, he added.“There was a significant amount of control and oppression that can happen in cases like this,” Camp said. “The mother was just unaware of what was actually going on.”A witness close to the family came forward to police with fourth-hand information that was “very surreal,” Camp said. The witness was extremely courageous and credible, he said, so police were able to start an investigation.The staff sergeant said there were a number of guns in the home, including a machine gun, so the situation was delicate.The accused has been co-operative so far and law enforcement agencies are trying to scrub the Internet of images of the girls’ abuse, he said. The victims are getting support to help them move on as best they can.“No child should have to endure what these three girls have survived,” he said. “There is no doubt they are going to have to manage this trauma to their lives for the rest of their lives.”The accused is to appear in an Evansburg courtroom on Monday to face charges that include five counts of sexual assault, two counts of incest, making child pornography and human trafficking.He also faces 17 firearms-related charges that were laid when his rural property was searched around the time of his arrest. Police said they seized roughly 40 restricted handguns and rifles, along with a machine gun and a dozen prohibited devices.