While protests in various cities occured without violence, a group of gun men used the occasion in Dallas to launch an assault against cops that resulted in at least five officers dead and others wounded.
The protests were against this week's killing by police of two black men in Lousiana and Minnesota.
The Dallas attack was not impromptu, so the motivation is not a clear other than the targeting of police in a way that is disturbing.
The shoot-'em-up left protestors in panic, although there are no reports of any non-police victims.
One shooter is dead and others are in custody,