.Just guessing. Nothing factual or for certain, just speculation on the cause of death. I would guess drowning. The water was waist high on a average tall man. I say he drowned them both in the water at the same time as he held onto them. And then dragged them up towards the cemetery where his car was parked.
There is a chance the LEOs found one body floating in the water, and put her on the bank, And went into the water to search for the other one they may had still been on the bottom. There was no strong current so they were able to walk the water arm and arm, shoulder to shoulder to find the other one in the dirty dark water......BUT ALL JUST A GUESS AND ASSUMPTION.
Imageries from this YouTube video
ALL JUST MOO. ALL SPECULATION AND ASSUMPTION. NOTHING BEING POSTED AS FACT. A MERE GUESS ON MY PART