Peter Bergen and David Sterman wrote for CNN about domestic terrorism:
Thursday's attack in Dallas provides a reminder that violent extremism and terrorist attacks are not the province of any one ideology. Instead, political violence has a long history in the United States and not just from people drawn to Osama bin Laden and his successors' vision of global jihad.
The suspected Dallas sniper who killed five police officers has been identified as Micah Xavier Johnson, a 25-year-old from Mesquite, Texas.
The Dallas shootings, like the one carried out last year by Dylann Roof on a black church in Charleston, South Carolina, that left nine people dead, were politically motivated.
Roof said he wanted to start a "race war," officials said, and he posted racist screeds on a white supremacist site.
Johnson "wanted to kill officers, and he expressed killing white people, he expressed killing white officers, he expressed anger for Black Lives Matter," Dallas police Chief David Brown said.