So sorry for your loss.
My dad was killed when I was 15 by a police officer no less. The cop was responding to a radio call and drove wrecklessly into my dad's car as my dad was making a left hand turn at the base of a blind hill the cop was flying over. The cop didn't have on his siren or lights...
Needless to say my mom sued and won. The officer was dismissed from the force soon after. He had a record of wreckless driving...
I lost my mom on Feb 12 due to Alzheimers.
As people have mentioned, go through his financial life and contact them regarding survivorship, probate and other such matters. Having a lawyer and information from the detectives will help.
It appears there won't be a murder investigation. Wow, to be taken out by your nephew. Just wow...
My prayers are with you and yours.