A mother says she “screamed like never before” when police told her that her two young daughters had been found dead in their father's apartment in Oak Bay, B.C., in December 2017.

Sarah Cotton began her testimony Monday at the trial for Andrew Berry, who has pleaded not guilty to second-degree murder in the deaths of his daughters, four-year-old Aubrey and six-year-old Chloe.

Cotton told a British Columbia Supreme Court jury that she began frantically calling and texting Berry after he failed to return their daughters at noon on Christmas Day as required by a court order.

His parents arrived at her house at 2 p.m. and Berry's father stayed behind while Cotton and Berry's mother drove to the man's apartment, knocked on the windows and buzzed the front door.

There was no light on inside and no answer, so Cotton and Berry's mother drove around searching parks and recreation centres. There was no sign of them and Berry wasn't answering his phone, so they went to police.

Cotton testified that she stayed at the station as officers visited Berry's home. When police collected Berry's father from her home and brought him to the station, she knew something was very wrong, she said.

“I knew at that point it wasn't good,” she said, adding she was also concerned when police from the nearby Saanich detachment began arriving at the Oak Bay station.

An officer asked her to go into the chief's office, and Cotton recalled that two officers sat her down in a chair and held on tightly as they delivered the news.

“They said Chloe and Aubrey have been injured. I thought, 'OK, but they're alive,' and then they said, 'They're dead,' ” Cotton said through tears.

“I screamed like never before. I was in shock.”

Earlier Monday, Cotton testified her relationship with Berry changed after the birth of their first child. By September 2013, when Berry was her common-law partner, their relationship was “very, very bad, very tense, very strained,” she said.

She said she called police and the Children's Ministry on several occasions, including to report suspected inappropriate touching of Aubrey, but police found no evidence the touching was sexual or criminal.

She also said Berry only paid child support for the first year after they separated in 2013. She contacted the family maintenance enforcement program and it began garnishing his wages in 2017, she said.

A court decision in 2016 said that Berry and Cotton would share parenting responsibilities. It also set out their schedule during the Christmas holidays and stipulated that they should only communicate by email except in case of emergency.

Several hours before Cotton was to drop the girls off on Dec. 21, 2017, she drove by his apartment and saw that it was dark. She remarked that Berry must not be home, to which Chloe replied, “Oh no, he's home. We use flashlights. It's just like camping.”

Cotton began to cry as she recalled realizing that Berry's electricity might have been shut off as he had resigned from his job months earlier. She said she asked the girls if they were cold when they stayed with their father and they replied that they weren't.

When she dropped them off, she said she didn't mention the electricity to Berry because she didn't want to provoke him in front of the girls.

“I wanted to keep the peace because it was Christmas,” she said, crying. “I was concerned for their well-being.”

She sent him two emails asking about the electricity, but he didn't reply, and she also asked Berry's mother to suggest to him that he stay with his sister.

Through tears, Cotton recalled the last time she saw the girls alive, when she returned to Berry's home a day after dropping them off to deliver a beloved stuffed toy of Chloe's. The little girl was wearing a pink dragon costume, and both girls asked when they could come back to her house, she said.

She replied that it was supposed to be three days but she was hoping she could get them back sooner.

“I told them that I loved them,” she said, sobbing.

Crown attorney Clare Jennings has told the jury that the father stabbed his daughters dozens of times each before attempting to kill himself.