GWEN IFILL: The nation is still grappling tonight with a series of tragedies, recent police killings of black men, and the sniper attack in Dallas.

It follows a long weekend of crowds confronting police and of mass arrests. Protesters are taking to the streets across the country. But in Dallas, the anger is tempered by grief for the five officers killed Thursday night.

Police Chief David Brown said today he is running on fumes.

DAVID BROWN, Chief, Dallas Police Department: My brain is fried. The memorization it takes to run a major city police department just on a normal process day with all things that happen is overwhelming. So this transpiring along with the normal things that are continuing to happen in the city is difficult at best.

GWEN IFILL: Doctors who tried to save Thursday's victims grew emotional at a hospital news conference today.

DR. BRIAN WILLIAMS, Parkland Memorial Hospital: This killing, it has to stop, black men dying and being forgotten, people retaliating against the people that are sworn to defend us. We have to come together and end all this.

GWEN IFILL: Meanwhile, detectives are reviewing more than 170 hours of body camera video, plus 300 witness and officer statements. They're searching for more background on Micah Johnson, the gunman who opened fire during an otherwise peaceful protest.

His parents told TheBlaze Web site today that his time in the Army Reserve wasn't what he thought it would be. They say he changed from a fun-loving extrovert into a hermit. Johnson died after a lengthy standoff with police.

Chief Brown said today he has no regrets about the decision to kill him with a robot-delivered bomb.

DAVID BROWN: We knew through negotiations this was the suspect, because he was asking, how many did he get? And he was telling us how many more he wanted to kill. This wasn't an ethical dilemma for me. I would do it again.

GWEN IFILL: In Baton Rouge, Louisiana, authorities arrested nearly 200 protesters demonstrating over the killing of Alton Sterling, captured on video last week, apparently by two officers.

Among those arrested, prominent Black Lives Matter activist DeRay McKesson, who was released Sunday.

DERAY MCKESSON, Black Lives Matter Activist: The only people that were violent last Saturday night were the Baton Rouge Police Department. The protesters remain peaceful both here and across the country. Again, I remain deeply disappointed in the Baton Rouge Police Department.

GWEN IFILL: Last night, Baton Rouge officers in riot gear kept protesters from entering Interstate 110 with what activists described as heavy-handed tactics. Hundreds also marched over the weekend in St. Paul, Minnesota, where picture was shot to death during a traffic stop; 21 officers were injured Saturday night.

Today, city leaders said they were caught off guard.

MAYOR CHRIS COLEMAN, St. Paul, Minnesota: The folks that were out there will all tell you that the restraint that our officers showed was second to none, but at some point when our officers are being bombarded by concrete and rebar, to the point where they are being injured, we need to respond.

GWEN IFILL: But community activist Robin Hickman said she wasn't surprised at all.

ROBIN HICKMAN, CEO, Soulmate Productions: We don't have relationships with our young people, our people who are just fed up, just have no hope. That's what you're going to get.

GWEN IFILL: Demonstrators also tried to block highways in Memphis and Los Angeles. Back in Dallas, police Chief Brown had a message today for protesters around the country.

DAVID BROWN: Become a part of the solution. Serve your communities. Don't be a part of the problem. We're hiring. We're hiring. Get off that protest line and put an application in. And we will put you in your neighborhood and we will help you resolve some of the problems you're protesting about.

GWEN IFILL: President Obama will travel to Dallas tomorrow for a citywide interfaith service, and meet with victims' families. He will be joined by Vice President Biden, as well as former President George W. Bush, and his wife, Laura.

Later, Dallas officials announced funerals for the five officers will begin on Wednesday.

We will return to Dallas and to the newly recharged national debate over policing and race after the news summary.