A quick definition of simultaneous death:

Simultaneous death means when two or more people die at the same time and it's impossible to tell who died first. It can happen in accidents or disasters. When someone dies, it means their body stops working and they can't breathe, move, or respond anymore. There are different types of death, like natural death from old age or sickness, accidental death from unexpected events, or violent death from human actions. Sometimes, when someone is missing for a long time, people might assume they are dead and have a legal process called presumptive death. In some cases, when someone dies because of someone else's actions, their family can take legal action called a wrongful-death action.