Twelve police officers have been shot with five killed after a sniper opened fire at a rally to protest the recent killings of two African-American men by police.

Downtown Dallas was empty and quiet, on this day after. Only television news crews were out in the harsh afternoon heat. It was a very different scene from less than 24 hours earlier.

"Chaotic, people were just scattered everywhere, all over. Running from all different angles and directions," said eyewitness Asha Harris.

A protest against two recent police shootings of African-American men in the U.S. states of Louisiana and Minnesota was wrapping up on Thursday evening when suddenly shots rang out. Officers here fell to the ground. A dozen of them in all were hit.

"I was walking and the sniper just started shooting. Man, like all of the cops were getting shot. Man, I just saw cops, like bending over, like, and it had to be live five or six cops, like they were all getting shot down, man. It was right after the rally, like we were just walking to the car, and then all of the cops," a witness said.

"What happened literally a minute later was so unsuspecting, it was so sudden and it was very tragic," said witness Sharay Santora.

Police say the suspect, 25-year-old Micah Johnson, a former Army vet, ran into a nearby parking garage and began exchanging gunfire with other officers. Police say he told them what had prompted the attack.

"He said he was upset about the recent police shootings, the suspect said he was upset at recent police shootings. The suspect said he wanted to kill white people, especially white officers," said Chief David Brown of Dallas Police Department.

Johnson refused to surrender. Hours later, police sent a robot containing a bomb into the garage and detonated it, killing the suspect. Today, a search of Johnson's home near Dallas turned up bomb-making materials, ballistic vests, rifles and a personal journal of combat tactics. The Dallas police chief called the attack a cowardly ambush and said his department was hurting.

"We are heartbroken. There are no words to describe the atrocity that occurred to our city. All I know is that this, this must stop," said Chief David Brown.

President Obama who's travelling in Europe right now. He did say that this assault was a vicious calculated attack on long enforcement. And apparently he's gonna make a big emphasis of police & community relations over the next week.