Not all the recent fires at black churches were arson. Here's what we know.

Since June 21, fires have been reported at six Southern churches that serve mostly African-American congregations. Investigators believe that two of these fires were intentionally set, and the cause of three others is unknown and under investigation.

These fires came to public attention a few days after the shooting that killed nine black members of Charleston's Emanuel AME Church on June 17 — which was itself a reminder of the long history of terrorism against black churches in America. Although church fires are not uncommon — and there is a lot we still don't know about the recent fires, some of which were accidental — many observers are fearful and anxious.