The person believed responsible for an attack targeting a Palm Springs fertility clinic Saturday posted rambling online writings before an explosion that investigators are treating as an act of terrorism, a law enforcement official told The Associated Press.

The FBI identified a person of interest in an explosion that killed one and injured four near the American Reproductive Centers in Palm Springs.

A car explosion rocked Palm Springs, Calif., Saturday, damaging a fertility clinic and blowing out windows in nearby businesses, officials said. There was at least one fatality.