How does a police investigation and charges work in the case of murder suicide?

I’m not asking for advice just details on how that situation even works.

like how you see in tv and movies and such. I mean a person was murdered but because the culprit is dead, you can’t really press charges on them. how far are they allowed to look into it.

this isn’t advice more just want to know what goes down but like in a regular murder you can question the suspect, find a motive, probably have them testify in court or ask witnesses or whatever.