What Happened to the Mackenzies?

Karen's former partner, andrew allen, was the father to almara and katrina. He claimed he'd been stuck in hall's creek during the time of the murders due to heavy rainfall that had flooded the roads leading in and out of town. A few days before the murders, shane eastef received an anonymous valentines day card featuring karen's handwriting. It read, what did i do? Care too much to be in your arms. Ain't so rough. Being yours could have been enough. What happened, babe? Scare you off like a diamond. You're just too tough.