Prosecutors in Platte County, Missouri, will seek the death penalty if Grayden Lane Denham is convicted in the horrific murders of his grandparents, sister, and infant nephew, CBS News reported Monday. The bodies of Russell Denham, 82, Shirley Denham, 81, Heather Ager, 32, and her 3-month-old son, Mason, were found shot dead and burning outside …