Mr Obama warned the attacks on police over racial bias will hurt the Black Lives Matter movement, saying there will always be people who make "stupid'' or "overgeneralising'' comments. Whenever those who are concerned about the failures of the criminal justice system attack police, they are doing a disservice to the cause, America's first black president told a news conference in Spain.
Johnson could not have conceived of an attack with greater potential to drive police and communities apart. People gathered in Dallas and other cities last Thursday night to protest the killings of two more black men - Alton Sterling in Baton Rouge and Philando Castile near St Paul - both shot by police who made snap judgements they posed mortal threats. Now police cannot help but feel more threatened, more embattled - and more justified in using force rather than seeking to de-escalate conflicts. The US faces a real risk of deepening a cycle of fear and mistrust with disastrous consequences on all sides.
Even as political leaders, protesters and law enforcement officials struggle to find common ground, there is an inescapable fear the US is being pulled further apart. People in interviews say the nation is feeling increasingly mired in bloodshed and blame. Despite pleas for compassion and unity, the US is fracturing along racial and ideological lines into angry camps of liberals against conservatives, Black Lives Matter against Blue Lives Matter, protesters against police. Citizens are asked to do the previously unthinkable - choose for whom they mourn.
The National Association of Police Organisations blames Mr Obama for waging a "war on cops''. On social media, others confront the discrepancies in everyday lives of black and white Americans, hoping understanding will lead to conversations and actions.
Black police officers are caught in the middle of the fracturing. The advice to black police is specific from a former Dallas officer: it is to collectively come out and speak about the various injustices in their departments. If they do not put pressure on their police departments to make reforms, there are fears the US will be doomed to a vicious cycle: police kill black people, leading to outrage and large protests, which in turn leads to deranged, lone wolf shooters who will start picking off the police.
Mr Obama is calling for calm, urging people to adopt a truthful, serious and respectful tone in the debate about race. So far, his calls appear to be falling on deaf ears. During the weekend, more demonstrations against the use of deadly force by police were held in several US cities, leading to hundreds of arrests. The figures are stark: young American black men continue to die at the hands of white police and now white police have died at the hands of an angry black man. Law enforcement officers were injured during the weekend demonstrations and there is no suggestion the anger is abating. Police departments are taking extra precautions and black families are warning their sons to take extra care when approached by law enforcement officers.
The US is gearing up for what is already a bitter presidential race. Republican nominee Donald Trump is playing the race card against Hispanics and Muslims rather than black Americans. But his calls to block immigrants will only play into the hands of aggrieved whites.
The US is stepping back to a world of hate and violence and its citizens seem powerless to halt the decline.
