A SNIPER who allegedly killed five police officers and injured seven others, as well as two bystanders, was a 25-year-old Army Reserve veteran.

Micah Johnson was reportedly killed after police sent a robot packed with explosives into the parking garage where he had hidden.

He spent several hours exchanging gunfire with police after first shooting at police officers who were protecting a Black Lives Matter protest where more than 800 people were marching.

Dallas Police Department said Johnson told officers "the end was coming" during the second shootout.

"During the search of the suspect's home, detectives found bomb-making materials, ballistic vests, rifles, ammunition and a personal journal of combat tactics," Dallas PD said in a statement.

Parts of the city where Johnson attacked officers remain a crime scene and are expected to be closed to the public until Wednesday.

Police had earlier identified the possibility of two snipers, but later said one person, a 25-year-old named Brandon Waller, was arrested on unrelated weapons charges.

At this stage only Johnson is believed to have carried out the attack.

The Dallas PD and the Dallas Area Rapid Transit took to social media to thank the thousands of people who attended prayer services and lay flowers for the officers who were killed.

Four DART officers were shot and one, 43-year-old Brent Thompson, was killed. The other injured officers were part of the Dallas Police Department. 

Speaking to media in Dallas early in the morning, Dallas Police Chief David Brown said the department saw no choice but to use the bomb robot and detonate it near Johnson.

"Our hostage negotiator did an exceptional job getting this suspect to talk before he died," he said. 

"The suspect said he was upset about Black Lives Matter.

"The suspect said he was upset at white people. The suspect stated he wanted to kill white people, especially white officers."

"The suspect stated he was not affiliated with any groups and he stated that he did this alone."

Officer Brown said Johnson also said he was upset about the two police killings that prompted the recent Black Lives Matter protests all across America.

Two African American men, Alton Sterling and Philando Castile, were shot by police and killed in the week before the Dallas protest where Johnson attacked officers and bystanders.

Officer Brown said the investigation was ongoing.  He paid tribute to Dallas PD and DART officers.

"We're hurting," he said. 

"Our profession is hurting. Dallas officers are hurting.

"We are heartbroken. There are no words to describe the atrocity that occurred to our city.

"All I know is that this must stop. This divisiveness, between our police and our citizens."

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