I would rule out strangulation in the apartment that evening based on the fact that I don’t think it would have been possible to have murdered your child silently in such a manner in a small apartment with the child’s mother and two siblings in attendance. Such an action would surely have caused some distress to those not doing thr murdering or being murdered so unless both parents had planned this murder and were both fully on board with it I think that bat-eared Mrs Fenn might possibly have heard some argument, panic, shouting, crying and screaming before, during or after such a hideous event.
And then we have the small matter of motive to consider.
But there really is no way to rule out strangulation.
Strangling a small child wouldn't be difficult, or make any noise, or leave any forensic trace in the apartment.
No, I'm sorry. I don't see how we can rule out the possibility that Brueckner strangled Maddie in the apartment.