The FBI has opened an “initial inquiry” – a procedural step before a full investigation – into this week’s fatal shootings of three young Muslims at a housing complex in Chapel Hill, N.C., near the University of North Carolina.

As the White House prepares to host a major summit examining the threat of violent extremism next week, the Southern Poverty Law Center today released a study of domestic terrorism that found the vast majority of this violence over the last five years has come “lone wolves”or “leaderless resistance”groups composed of no more than two people.