Man who shot Dallas police wanted to kill more officers - chief

Explosives found at the home of gunman Micah Johnson suggested he had been plotting a larger assault, said authorities, who were still trying to understand a message he wrote in his own blood on a wall before being killed by a bomb-equipped robot sent in by the police.

"We knew through negotiations this was the suspect because he was asking us how many did he get and he told us how many more he wanted to kill," Dallas Police Chief David Brown told reporters on Monday.

The attack on Thursday night came at the end of a demonstration over police shootings that had been prompted by incidents earlier in the week in which police in Baton Rouge, Louisiana, and St. Paul, Minnesota, killed two black men.

Johnson, a 25-year-old African-American, told police negotiators during an hours-long standoff that he had been angered by those deaths and had wanted to "kill white people."

The deaths in Baton Rouge and St. Paul were the latest in a series of high-profile and controversial killings of black men by police in cities including New York, Ferguson, Missouri, Chicago and Baltimore.

Even as officials and activists condemned the shootings and mourned the slain officers in Dallas, hundreds of people were arrested on Saturday and Sunday as new protests against the use of deadly force by police flared in U.S. cities.

Scores of people were arrested in Baton Rouge on Sunday after authorities warned that violence during street demonstrations would not be tolerated.

Brown said a search of Johnson's home showed the gunman had practiced using explosives, and that other evidence suggested he wanted to use them against law enforcement officers.