§ 1651.11 Simultaneous death.
Primary source
Verbatim text below is from the Electronic Code of Federal Regulations (eCFR), a public-domain U.S. government work. Always verify the current version with the eCFR before relying on it for any legal matter.
Full Text
If a beneficiary dies at the same time as the participant, the beneficiary will be treated as if he or she predeceased the participant and the account will be paid in accordance with § 1651.10. The same time is considered to be the same hour and minute as indicated on a death certificate. If the participant and beneficiary are killed in the same event, death is presumed to be simultaneous, unless evidence is presented to the contrary.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.