To the shock of police departments across America, it has happened again.
Less than 24 hours after Dallas was burying the fifth police officer killed in an ambush in that city, and Louisiana is now in mourning.
The attacks seem to be uncannily similar.
In both Dallas and Baton Rouge, African-American gunmen - veterans of Afghan or Iraqi deployments and with no criminal or extremist profile - have opened fire on police officers.
Both assaults came out of the blue, catching police by complete surprise, and appear to be warped revenge for police shootings of black men.
The gunman this time was Gavin Long, a 29 year-old former US Marine with an active social media profile.
For police departments, this is a nightmare. One extremist with a Black Power anti-police agenda is a rouge individual. Two could be a pattern.
It feeds into a narrative that America is facing a racial division that is spiralling out of control.
The President is urging calm, and asking political leaders to try and build bridges between police officers and minority communities.
But with the Republican Party convention beginning in a few hours, Donald Trump is not listening.
He continues to engage in an inflammatory Twitter rant, calling all of America a "divided crime scene."
He even conflates the attacks on police with the threat of ISIS terrorism. It is reckless and dangerous rhetoric. And it may be working.
Trump is trying to define his bid for the White House as an anti-chaos campaign, based on "law and order."
Today's convention theme is "Keep America Safe Again."
Undoubtedly, many Americans fear that racial and political tension is rising and ready to explode.
What is quite clear is that there is a powerful and incendiary politician ready this week to exploit that anxiety for his own electoral gain.