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The Department of Justice held a news conference Friday, with Attorney General Loretta Lynch addressing the ambush.
VIDEO: Chief Brown describes sniper suspect's motives
Search warrants are being executed now at the Johnson family home.
"The suspect said he was upset about Black Lives Matter. He said he was upset about the recent shootings," Brown says. "The suspect said he was upset at white people. The suspect stated he wanted to kill white people and especially white officers."
"The suspect stated (police officers) will eventually find the IEDs. The suspect stated he was not affiliated with any groups and he stated that he did this alone."
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Brown also said the alleged motive was not "a reason or legitimate reason to do harm to anyone."
The incident marks the deadliest day for law enforcement since the September 11, 2001 terror attacks. It also drew a comparison with the November day in 1963 when a U.S. president was slaughtered by a sniper on a Dallas street only a few blocks away.
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"We don't exactly know the last moments of his death but explosives did blast him out," Rawlings told The Associated Press.
He said police swept the area where the standoff took place and found no explosives.
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