He suffered personal tragedy when his sister Debbie was killed in a dune buggy accident .
This did not deter Unser ; and a year later , he competed in his first Indianapolis 500 , finishing 9th .
He suffered personal tragedy when his sister Debbie was killed in a dune buggy accident , but this did not deter Unser ; and a year later , he competed in his first Indianapolis 500 , finishing 9th .