At 12.35 a.m. on 5 July, the night after Independence Day, police in Baton Rouge accosted 37-year-old Alton Sterling who was selling CDs in front of the Triple S Food Mart, a convenience store in a poor neighbourhood. Mobile phone footage, taken by members of an organisation that monitors police violence against civilians, shows two police officers pinning Sterling down and shooting him at point-blank range, multiple times. We see Sterling’s blood spread rapidly across his red shirt. We see a man die. The following day, not long after nine o’clock in the evening, in a suburb of St Paul, Minnesota, a 32-year-old man who had been shot several times by police was having his last moments of life streamed on Facebook by his girlfriend, Diamond Reynolds. Reynolds tells us that the police officer told them they were being stopped for a broken tail-light. When the police asked for Philandro Castile’s car registration, Reynolds says, Castile told the officer that he had a permit to carry a gun. The officer asked Castile to raise his hands. He complied. The officer shot Castile several times. Then Reynolds lets ‘the whole world see’ what the police have done to her boyfriend. We watch Castile moan. We see blotches of blood on his shirt. We see him lie still. And we hear Reynolds’s calm and civility: ‘Please don’t tell me he’s gone. Please, officer, don’t tell me that you just did this to him.’ Castile was a surrogate father to Diamond’s four-year old daughter, in the backseat while the terror unfolded. As her mother was removed from the car, handcuffed and placed in the back of a police car, the little girl can be heard saying on the video: ‘I’m here for you mommy.’ In September 1955, Mamie Till wanted to let the world see what a Mississippi lynch mob had done to her 14-year-old son, Emmett. The images have stayed with us for more than half a century: a monstrous and bloated corpse – beyond immediate recognition – lying on a porcelain slab in a funeral parlour on Chicago’s South Side. It looked like something from outer space, many said, as they passed Emmett Till’s bier or saw photographs of his mutilated face in black magazines and newspapers. Each succeeding generation of African Americans has encountered the grotesque images with horror. Now there are 21st-century images of the inhumane treatment of black bodies for future generations to witness. The videos of Sterling and Castile join the mobile phone footage of the choking to death of Eric Garner on Staten Island on 17 July 2014. He speaks above a whisper – ‘I can’t breathe’ – as life is squeezed out of him. The shooting to death of John Crawford on 5 August 2014, as he talked on the phone with his girlfriend in a Walmart outside Dayton, Ohio, was recorded on the store’s surveillance video. The police car dash-cam video documenting the shooting of 17-year-old Luquan McDonald on 20 October 2014 was suppressed by the Chicago police, the Cook county prosecutor, and possibly Mayor Rahm Emanuel for over a year. It shows McDonald twirling to his death in a hail of police bullets. The killings of Sterling and Castile triggered a wave of protests against police brutality in cities across the United States on Thursday, 7 July. During a demonstration in Dallas, a 25-year-old sniper aimed his assault-style rifle at the police, killing five – Lorne Ahrens, Michael Krol, Michael Smith, Brent Thompson and Patrick Zamarripa – and wounding seven. The assassin, Micah Johnson, an African American army reserve veteran of the war in Afghanistan, may have bought the weapon through connecting with a seller on Facebook. According to the Dallas police chief, David Brown, Johnson was upset about the recent killings of black men by police and wanted to kill white people, especially white police officers. The police used a bomb-carrying remote-controlled robot to kill Johnson, who claimed to have planted bombs around the city. What the assassin did in Dallas was a reverse act of white supremacist violence, a form of hate that hate produced. On 8 July, I took my nine-year-old son on a planned trip to the National Civil Rights Museum, built in Memphis around the former Lorraine Motel, the site of Martin Luther King’s assassination in 1968. The museum was full, the mood sombre. We saw flashes of King’s ‘I Have a Dream’ speech and listened to the familiar lines of ‘let freedom ring’ and the unfamiliar ones that were more resonant that day: When will we be satisfied? We will never be satisfied as long as the Negro is the victim of the unspeakable horrors of police brutality. We had difficult conversations – not the first or the last – about America’s racist past and present. I thought about assassins’ bullets, then and now, and the slaughter of innocents in Memphis, Baton Rouge, St Paul, Dallas, as we passed the balcony where King collapsed to his death from a sniper’s bullet. During the memorial service for the slain officers in Dallas on 12 July, President Obama said that despite the setbacks of last week’s carnage, the nation has progressed since the 1960s. Obama offered comfort, hope, regrets. ‘We are not divided as we seem,’ he declared. But there are deep divisions. Like the Ferguson police department’s response to protesters after Michael Brown’s death-by-police in 2014, the Baton Rouge police department responded to Black Lives Matter demonstrations after the Dallas massacre as if they were prepared to do battle against an invading army. They used military armour, and arrested more than 180 people for such minor infractions as obstructing traffic. During one confrontation a photographer captured the image of Ieshia Evans, a lone protester standing her ground with composure as officers in riot gear rush toward her. ‘We don’t have to beg to matter,’ Evans later told a reporter. ‘We do matter.’ ‘I’ve seen how inadequate words can be,’ Obama told those grieving in Dallas, ‘in bringing about lasting change’ in addressing racism in the United States. Many Americans, who believe that ‘all men are created equal and endowed with inalienable rights’ and see those rights unequally distributed, continue to weep despite recognitions of progress. And some of us recall what Frederick Douglass told America about America the day after 4 July 1842: ‘For revolting barbarity and shameless hypocrisy, America reigns without rival.’