Dallas police headquarters on security alert after threat

“That man went through a lot”, said Ron Franklin, one of the many Dallas residents who came to pay tribute at a memorial outside the police headquarters.

“We had negotiated with him for about two hours, and he just basically lied to us – playing games, laughing at us, singing, asking how many (police officers) did he get and that he wanted to kill some more and that there were bombs there”, Brown said, “so there was no progress on the negotiation”.

President Barack Obama and Texas Gov. Greg Abbott asked for the public’s prayers.

Minnesota Governor Mark Dayton has said he did not believe Castile would have been shot dead had he been white, remarks which were criticized by state law enforcement groups.

Vice President Biden will also attend, the White House said Sunday, as will President George W. Bush and his wife. Police initially suspected more than one shooter.

Protesters will not be “allowed to incite hate and violence, to engage in unlawful activities”, he added. Others said they don’t expect police to use robots like this except in extreme cases.

“I’m feeling very haunted, very sad”, said Lorena Ambrosio, 27, a Peruvian American and freelance artist, “and just angry that black bodies just keep piling and piling up”.

He said a search of Johnson’s home turned up signs the gunman had practiced using explosives, and that other evidence suggested he wanted to use them against law enforcement targets. Among them was activist leader DeRay McKesson, who livestreamed the incident.

Mckesson was freed on bond on Sunday. The police department said police headquarters is not in lock down, disputing some reports in the media.

Both shootings were caught on camera and sparked global outrage.

Johnson’s Facebook photo showed him wearing a dashiki and raising his fist over the words “Black Power”.

In downtown Dallas on Sunday morning, the police continued to block access to more than 20 square blocks as investigators entered the third day of their inquiry.

Shortly after he took the helm of the Dallas police force in 2010, his 27-year-old son, David Brown Jr, fatally shot an officer and another man while high on drugs, before being killed by police.

Peaceful marches attracted large crowds in major USA cities, but became especially unruly in St. Paul, Minnesota and Baton Rouge, Louisiana, where police killed the two men.

Bomb-making materials, weapons and ammunition were found in Johnson’s home.

But in his six years as police chief, Brown, 55, has experienced profound tragedy of his own.

“This suspect had been practicing explosive detonations and the materials were such that they were large enough to have devastating effects throughout our city”, Brown said.

Johnson had practised military-style drills in his garden and trained at a private self-defence school that teaches special tactics, including “shooting on the move”. “I began to feel it was a split second before he would charge us and take out many more before we could kill him”.

Authorities say he specifically targeted white officers in retaliation for black deaths at the hands of police. The deaths have fomented unrest from Ferguson, Missouri, to Baltimore and heightened calls for greater accountability of police, particularly in the urban, majority-black neighborhoods they patrol.

Johnson, who was apparently injured in a shoot-out with police, wrote the letters “RB” and other markings.