mystery book about new wife/stepmother murdering husband/ kids’ father

I think it began with the murder - father is on camping trip with young son(?) and is hunting and gets shot in the woods. turns out it was a hit man hired by the new wife. adult daughter nicknamed something boyish maybe Bucky(?) is suspicious of stepmother and with help of father’s friend looks into her. I wanna say the stepmothers name was something starting with a V but maybe that’s just the typical villain black widow type character name. have not been able to find this book since i read it as a teen so hopefully someone knows it!!