Unnatural deaths are covered by life insurance, depending on the policy you own. For example, the life insurance policy can pay out a death benefit to the designated beneficiaries if an insured person passes away due to an accident such as a motor vehicle accident, drowning, etc.
Life insurance is meant to provide coverage should you pass away whether it be due to natural causes, accident or illness. There are, however, circumstances such as fraud or committing suicide within 2 years of the policy issue date, when a policy will not payout. For a detailed list of exclusions, it is always good to check with your life insurance company.