The blast killed Denise McNair, 11, and Addie Mae Collins, Cynthia Wesley and Carole Robertson, all 14. They died in a basement room of the church while preparing for Sunday services.

In the 1970s, former Klansman Robert E. Chambliss was convicted of the bombing and sentenced to life in prison, where he died almost a decade later.

The FBI reopened its investigation into the bombings in the 1990s at the urging of Black pastors. Two former Klansmen, Thomas Blanton Jr. and Bobby Frank Cherry, were then indicted.

Spencer almost didn't make it to the trial. He was hospitalized with heart failure while traveling and persuaded his cardiologist to accompany him to the trial so he could testify.

Spencer had been with the Tampa FBI office just a few weeks when he was assigned to join agents from across the country to work on the bombing case. He stayed with the Tampa FBI office until 1977, when he retired.

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