Cops Investigating Mysterious Initials Scrawled by Dallas Gunman and Poring Over Video Footage

— -- Police in Dallas are trying to piece together what happened in the deadly attack on police officers there last week — downloading and poring over 170 hours of video and trying to get to the bottom of initials R.B. scrawled by suspected gunman Micah Johnson in two locations during his final hours, Dallas Police Chief David Brown said this morning.

"We don't know the scope of his plans yet," Brown said.

"We're going to follow every lead until it's exhausted, until I'm satisfied this was the lone person," he said. "I may be overly concerned about this, but I'm highly protective of cops, and I want to make sure there's nobody else out there that has something to do with this."

Brown said he and his family received death threats almost immediately after the Thursday night attack, which left five officers dead and 11 other people injured.

"My particular threat was a post from a private Facebook to our Dallas Police Department Facebook," he said. "We've been unable to identify the source of the threat, but we're taking it very seriously."

"As a policing family here in Dallas and across the country, there is a heightened sense of awareness around threats we received all over the country," he said.

"I don't want to just single out me. Everyone's experiencing the same type of awareness, increased awareness, because of people who, in my opinion, are not stable, who could do grave damage to us. So we're all on edge," he said.

Johnson is suspected of opening fire on officers during a demonstration against police brutality in Dallas last week. Police said he was looking to kill white people, especially police officers, and was upset about two recent fatal police shootings of black men.

He was killed by police after a standoff using a bomb delivered by a robot.

The bomb technician said the gunman wasn't a novice and "knew what he was doing," Brown told reporters today.

Brown said 13 officers used force against the suspect, with 11 using their firearms and two using the explosive device.

The robot used to deliver the explosive device was purchased in 2008 for approximately $151,000. Brown said there's partial damage to the extension arm of the robot but it is still functional for future operations.

In the wake of the attack, he said counseling services are important for his officers.

"We're the last to say we need help," Brown said.

Funeral services for three of the slain officers have been set for this week, the Dallas Police Department said. Arrangements for the other two officers are pending.

"We're asking cops to do too much in this country," Brown said today. "Every societal failure, we put it off on the cops to solve. Not enough mental health funding. Let the cop handle it. Not enough drug addiction funding. Let's give it to the cops."

He said, "Seventy percent of the African-American community's being raised by single women. Let's give it to the cops to solve that as well. That's too much to ask. Policing was never meant to solve all those problems."

"I just ask for other parts of our democracy, along with the free press, to help us, to help us and not put that burden all on law enforcement to resolve," he said.