Damage shown from blast that stopped police-killing sniper

[Matrosov]

87. He claimed he had planted explosive devices throughout Dallas

There was an excellent article that detailed some of the police negotiations with him. I'll try to find it again, meanwhile these have bits and pieces. http://www.latimes.com/nation/la-na-dallas-police-shooting-20160708-snap-story.html

Investigators discovered bomb-making materials, rifles and a “personal journal of combat tactics” in the home of the black former Army reservist who struck during a demonstration against the shooting of two black men by police officers in Minnesota and Louisiana.

“The suspect said we will eventually find the IEDs,” Brown said, a reference to explosives. “He wanted to kill officers. And he expressed killing white people, killing white officers, he expressed anger for Black Lives Matter.”

“We saw no other option than to use our bomb robot and place a device on its extension to detonate where the suspect was,” Brown said. “Other options would have exposed our officers to grave danger.”

http://fox6now.com/2016/07/11/writing-in-blood-threats-of-bombs-the-latest-on-dallas-shooting-investigation/

During his hourslong standoff with police, Johnson said he was ready to kill more cops with bombs, Dallas police Chief David Brown told CNN.

“We had negotiated with him for about two hours, and he just basically lied to us — playing games, laughing at us, singing, asking how many (police officers) did he get and that he wanted to kill some more and that there were bombs there,” Brown said.

A search of the gunman’s home revealed he had plenty of supplies to make explosives. Brown said police found bomb-making materials and a journal that suggested Johnson had been practicing detonations and appeared ready to take aim at larger targets.

It was enough, Brown said, to have “devastating effects on our city.”

From what all I've read, my understanding is that they tried to negotiate with him for several hours, when he made the threat of wanting to kill more officers and of having planted explosive devices throughout the city. Police had searched his home during the negotiations and found bomb making materials there, which led them to believe there was a good chance he wasn't bluffing. They worried about the possibility of him detonating the devices remotely, and at that point they gave him the chance of surrendering peacefully 'or else.' He said he wasn't going to be taken alive.

So I don't get the sense that they killed him out of revenge or impatience. There was urgency because of his bomb threats, and he refused the final ultimatum to surrendering. If they'd just gotten bored or had killed him while he was trying to surrender, I'd have agreed that it was an execution.