Baton Rouge: The black US Marine Corps veteran who shot dead three police officers in Louisiana's capital specifically targeted them, police said on Monday, as the United States reeled from the latest deadly violence involving police and black people.
Another officer who was wounded in Sunday's shootings in Baton Rouge was fighting for his life, the state's governor said.
The city had been the scene of repeated protests against police violence following the July 5 fatal shooting by officers of Alton Sterling, a black man outside a convenience store.
The Baton Rouge gunman has been identified as Gavin Long, a 29-year-old from Kansas City, Missouri, who served in the Marines for five years, including a 2008 deployment in the Iraq war.
Long, dressed in black and armed with a rifle, was shot dead on Sunday morning in a gunfight with police.
Racial tension in the United States has been especially high since a black former US.
Army Reserve soldier fatally shot five Dallas police officers who were patrolling a protest over the police shootings of Sterling and another black man in Minnesota.
"It's a very tough situation here, an attack on the very fabric of society," Louisiana Governor John Bel Edwards told MSNBC on Monday.
Louisiana State Police spokesman Lieutenant J.B.
Slaton told the New York Times on Monday that a preliminary investigation shows the Baton Rouge gunman "definitely ambushed those officers."
"We are still trying to find out what his motive was, and that's going to be part of our investigation.
But we believe he was targeting those officers," Slaton said.
Social media postings linked to an individual named Gavin Long and a Kansas City address, which was cordoned off by police, included a July 10 YouTube video saying he was fed up with mistreatment of blacks and suggesting only violence and financial pressure would bring change.
The dead officers were identified as Montrell Jackson, 32; Matthew Gerald, 41; and Brad Garafola.
Edwards said one of the wounded officers was fighting for his life while a second underwent surgery and needed further surgery on his neck.
A third officer who had a graze wound to his neck was released from a hospital on Sunday.
US Attorney General Loretta Lynch, in remarks prepared for a conference of black law enforcement officers in Washington, said federal law enforcement agents from the FBI, the Bureau of Alcohol, Tobacco, Firearms and Explosives, and the US Marshals Service were on the scene in Baton Rouge.
"At the Department of Justice, we are determined to do everything we can to bridge divides, to heal rifts, to restore trust, and to ensure that every American feels respected, supported, and safe," Lynch said in her remarks.
Louisiana's capital is a city with a long history of distrust between black residents and law enforcement that has been inflamed by Sterling's death.
For many in Baton Rouge, the police have been viewed as overly aggressive and unrepresentative of a city where more than half the 230,000 residents are black.
Lynch, who is black, quoted remarks by Jackson, a black officer killed in Baton Rouge, that he got "nasty, hateful looks" in uniform and felt that some people considered him a threat when he was out of uniform.
She quoted him as saying, "Please don't let hate infect your heart."
Lynch said that "if we are truly to honor his service and mourn his loss - and the loss of his friends and colleagues, and of too many others who have been taken from us - we must not let hatred infect our hearts."
At the same event, Lynch's predecessor as attorney general, Eric Holder, said that "an attack on a police officer is an attack on society itself and can simply not be condoned." With America's permissive gun policies, Holder also noted US police often find themselves confronted by people armed with military-grade weapons.
He urged law enforcement authorities and others to "speak up" about the need for gun control.
"We live in troubled times, beset by violence directed at those who are sworn to protect us, necessary community law enforcement relations that are frayed, awash in high powered weapons of war and subject to rhetoric that is too often overheated and factually inaccurate," Holder said.
On the July YouTube video attributed to Long, he said he was speaking from Dallas after going there to protest.
"It's only fighting back or money. That's all they care about," he said to the camera."Revenue and blood, revenue and blood, revenue and blood."
In a separate video, he hinted that should anything happen to him, he wanted viewers to know he was not affiliated with any particular movement or group.
The violence also has heightened security concerns, notably in Cleveland, where Donald Trump is expected to get the presidential nomination at the Republican National Convention, and Philadelphia, where Democrats are to nominate Hillary Clinton for the November 8 election.