The US police have found bomb-making material, rifles, ammunition and a combat journal at the home of the suspect in the Dallas shootings, Micah Johnson.
The 25-year-old suspect died after a long stand-off with police in central Dallas.
Five police officers were killed and seven wounded in a hail of gunfire during a protest on Thursday against the shooting of black men by police.
Dallas Mayor, Mike Rawlings said officials believed he was “the lone shooter.”
“We believe now the city is safe,” the city mayor said at a news conference late on Friday.
Different protests broke out after this week’s deaths of Philando Castile in Minnesota and Alton Sterling in Louisiana.
Officials said on Friday that a number of gun attacks on police officers and civilians had occurred in the aftermath of the deaths in Minnesota and Louisiana.
Protests against police killings were also held in other US cities, including Houston, New Orleans and San Francisco.
In Baton Rouge, Louisiana, protesters chanted “no justice, no peace, no racist police.”
There have been some arrests at the rallies, but again they have been peaceful.
A Black Lives Matter march was also held in London.
In Dallas, Mayor Rawlings addressed thousands at a vigil to honour the police officers, urging Americans to “step up” to heal the nation’s racial wounds.
Mr Rawlings said the suspect had been given a choice of “surrendering without harm or remaining in place”, adding that he chose “the latter.”
Johnson, a member of the US Army Reserve from 2009 to 2015 who had served in Afghanistan, had no criminal history.
Police chief, David Brown said the suspect had told a negotiator that he had wanted to kill white people, especially white police officers, because he was angry about the recent shootings of black men by police.
Mr Brown added that the man had said he was not affiliated with any groups and had acted alone.