I can’t see the foul turkey as a motive...but certainly the fact that Denise and Jim were both killed could indicate a work-related motive of some sort. There would be no reason to kill Jayme.
Taking her, if she was a witness, makes no sense to me though, as my big question remains the same...what on earth does one do with someone else’s teenager? If you mean to kill her, you do it right then, it would have taken one additional second. Having a teen on your hands would be a nightmare if you intended to blend right back into work, routine etc...and how would it ever be resolved? Also, someone from work could have found out easily enough there would be a child in the home. All of it adds up to zero, for me.