Friend said murdering mum's 'mission in life was her two children'

When Catherine Knowles heard the news that Christy Sheats had shot and killed her two daughters, she ‘immediately thought, “It's a mistake.”’

‘Her mission in life was her two children,' Knowles, who was a close friend of Sheats, told PEOPLE.

‘I kept telling myself, “This is not the same person,”’ Knowles said. 

Adding, 'She loves her daughters. I have no idea what could possibly make a mother who loves her daughters as much as she did – what could cause a person to snap?'

‘This is such a tragedy,’ Knowles said. ‘The part of Christy that I knew was a very kind, loving mother. Within 20 seconds of meeting her, we were talking about her being a mom. That was her mission in life, that was her everything – her two daughters.’

According to a press release from the Fort Bend County Sheriff's Office, Christy Sheats “convened a family meeting” in the living room of her Texas home before opening fire on Madison, 17, and Taylor, 22.

Madison collapsed and died at the scene, while her sister, Taylor, was airlifted to hospital where she later died from her injuries.

It was later reported that Taylor Sheats was to be married today.