Zack's Dad
Probable: maintenance-related inflight engine failure while holding at low altitude pending clearing of rain over runway. Probable: PIC stalled out during unpowered glide ditch phase due error under stress or weather-related effects.
Most likely though, an inexperienced young pilot who inadvertently got himself into weather which he should not have been in, with the all too common result of disorientation, leading to a spiral dive which was not recovered in time.
The weather was atrocious, and nobody should have been flying a single in those conditions.
I do feel very sorry for you and your loss. Zack was a good bloke. Unfortunately he got himself into a situation that he was ill-equipped to deal with.