If the perp had a vehicle nearby, and he had planned the kidnapping in advance, he could have quicky bundled JBR up--maybe place her in a large canvas bag, and left the house and got into his vehicle.

This could indicate someone on foot---someone that panicked and killed her--and was going to remove her body from the house...but when he couldn't get her out of the window in the suitcase, he just tossed her in the cellar room. I don't think he originally wanted to leaved her body in the house. IMO, I think he reacted in panic.