A black US military veteran of the Afghan war who said he wanted to "kill white people" opened fire in a sniper attack in which five police officers were slain at a protest decrying police shootings of black men, officials said.
Seven other police officers and two civilians were wounded in the ambush in downtown Dallas on Thursday night (local time), officials said. Police killed the gunman, identified by a United States government source as 25-year-old Micah Xavier Johnson, with a bomb-carrying robot after cornering him in a parking lot, ending an hours-long standoff.
NEW: #Dallas shooting suspect Micah Xavier Johnson served in the U.S. Army for nearly 6 years, the Army says https://t.co/r7syDik5cp
— CBS News (@CBSNews) July 8, 2016
A search of Johnson's home in the nearby suburb of Mesquite found "bomb-making materials, ballistic vests, rifles, ammunition and a personal journal of combat tactics," Dallas police said in a report on Friday. Police said Johnson had no previous criminal history.
Dallas Mayor Michael Rawlings said Johnson had written "manifestos" on military-style tactics, and social media postings left by Johnson showed he subscribed to a militant black nationalist ideology.
Thursday's attack came at the end of an otherwise peaceful march to protest police killings of two black men this week in Minnesota and Louisiana, the latest police killings of black men over the last two years that have triggered outrage, soul-searching and debates over the role of race.
In Dallas, hundreds of screaming demonstrators ran for safety as police officers patrolling the rally took cover, believing initially that they had come under attack by several shooters. By late afternoon on Friday, however, investigators had concluded that Johnson, armed with a rifle, was the lone gunman.
"At this time, there appears to have been one gunman, with no known links to or inspiration from any international terrorist organization," US Homeland Security Secretary Jeh Johnson told reporters in New York.
In Dallas, Rawlings said the shooting "came from one building at different levels from this suspect."
One man was arrested on "unrelated weapons charges" at the scene, and several people were detained for questioning, but police said they were released by day's end on Friday.
Still, Governor Greg Abbott and other officials said they were looking for evidence of any possible co-conspirators.
The ambush marked the highest death toll for US police in the line duty from a single event since the September 11, 2001, attacks.
GUNMAN ANGRY ABOUT POLICE KILLINGS
The attack was certain to complicate rising tensions between minority communities and law enforcement following a string of high-profile killings of unarmed black men at the hands of police across the country over the past two years, giving rise to the Black Lives Matter protest movement.
The violence came just over a week before the start of the Republican National Convention in Cleveland, where Donald Trump is expected to become the party's official nominee, and police in Cleveland on Friday tightened their security plan for the convention. Other police departments across the country, including New York, Chicago and St. Louis, responded to the attack by requiring officers to patrol in pairs rather than alone.
Dallas Police Chief David Brown called Thursday's ambush "a well-planned, well-thought-out, evil tragedy." He added:"We are determined to not let this person steal this democracy from us."
During lengthy negotiations with police, the gunman told police he was angry about the Louisiana and Minnesota killings, Brown told reporters.
"The suspect said he was upset at white people. The suspect stated that he wanted to kill white people, especially white officers," said Brown, who is African-American.
A profile of Johnson's political inclinations also began to emerge. He posted a rant against white people on a black nationalist Facebook group called Black Panther Party Mississippi last Saturday, denouncing the lynching and brutalizing of black people.
"Why do so many whites (not all) enjoy killing and participating in the death of innocent beings," Johnson wrote in a post above a graphic video of a whale-killing, comparing it to the treatment of black people in the US.
In what appeared to be his own Facebook page, Johnson was portrayed with the red, black and green flag sometimes known as the Black Liberation flag. His profile photo showed him with his clenched fist in the air in the familiar Black Power salute.
The US Army said Johnson had served as a private first class in the Army Reserve and was deployed to Afghanistan from November 2013 to July 2014. It said Johnson served from March 2009 to April 2015 and was a carpentry and masonry specialist with the 420th Engineering Brigade based in Texas.
Thousands of people took to the streets in US cities on Friday to denounce the fatal police shootings of two black men. Protesters clogged roadways in New York City, Atlanta and Philadelphia on Friday evening, and events also were planned for San Francisco and Phoenix.
'HEARTACHE AND DEVASTATION'
President Barack Obama called the shooting "a vicious, calculated and despicable attack on law enforcement."
Obama, who was in Poland for a NATO summit and has been stymied by the Republican-led Congress in his bid for new gun control laws, added: "We also know when people are armed with powerful weapons unfortunately it makes attacks like these more deadly and more tragic."
Three of the slain officers were identified on Friday. One was Brent Thompson (43), who joined the Dallas Area Rapid Transit police department in 2009, according to police. Another was Patricio Zamarripa (32), a US Navy veteran, according to his family. Also killed was Michael Krol (40), according to the Wayne County Sheriff's Office in Michigan, where he used to work.
Reverend Jeff Hood, an organiser of Thursday night's protest in Dallas, said he had been chatting with some of the police officers on the street when gunfire erupted.
"I saw what I believe were two police officers that went down. I didn't know what to do," Hood told reporters on Friday. "If we continue to turn to violence, we are going to continue to see heartache and devastation."
A string of killings of black men and boys by police in cities including Ferguson, Missouri, New York, Baltimore, Chicago, Cleveland, Tulsa, Oklahoma and North Charleston, South Carolina gave rise to the Black Lives Matter movement against excessive police force.
A Twitter account describing itself as representing the Black Lives Matter movement sent the message: "Black Lives Matter advocates dignity, justice and freedom. Not murder."
Police in Dallas said they were questioning two occupants of a Mercedes they had pulled over after seeing a man throwing a camouflage bag inside the back of the vehicle, which then sped off on a downtown street. A woman was also taken into custody near the garage where the standoff took place.
The Dallas shootings happened as otherwise largely peaceful protests unfolded around the United States after the police shooting of Philando Castile, a 32-year-old black man, on Wednesday during a traffic stop near St. Paul, Minnesota.
The day earlier, police in Baton Rouge, Louisiana, shot dead 37-year-old Alton Sterling while responding to a call alleging he had threatened someone with a gun.
Both killings were captured on video, with Castile's girlfriend broadcasting the bloody aftermath of his shooting live on the internet.
Cleveland police officials have tightened their security plan for the July 18-21 Republican National Convention as a result of the shootings of in Dallas, Deputy Police Chief Ed Tomba said.
