When shots rang out in Dallas last week, police zeroed in -- wrongly -- on men in camouflage gear carrying powerful military-grade rifles.

People can carry such guns openly under Texas law, a provision now under scrutiny for complicating police work in a moment of acute crisis.

About 20 such armed men had joined a march Thursday over the deaths days earlier of two black men at the hands of police, in Louisiana and Minnesota. Some even carried gas masks and wore bulletproof vests.

The problem began when Micah Johnson, a black 25-year-old one-time Army reservist, launched an ambush attack with an assault rifle, targeting white police monitoring the rally.

When the chaos that engulfed downtown Dallas was over, Johnson had killed five police and wounded seven others, plus two civilians. He told police negotiators before being killed by a robot bomb that he wanted to kill white cops.

When Johnson initially started shooting, police immediately faced the dilemma of distinguishing armed but non-hostile protesters from the actual shooter or shooters in a moment of violent mayhem as crowds scurried for safety.

Most US states, including Texas, let people carry long arms -- rifles and shotguns -- in public with no need for a permit.

Since January, people in Texas can also carry handguns openly in public, but for that, they do need a license.

Dallas police chief David Brown questioned the logic of carrying long firearms at a protest rally.

"Doesn't make sense to us," Brown said. "But that's their right in Texas."

"We don't know who the good guy is versus the bad guy," he said.

Texan gun owner Joe Coker said Dallas police have not received enough credit for how well they handled the crisis Thursday: not getting trigger-happy as a man with an AR-15 assault rifle opened fire and others with those same weapons were running through the streets seeking cover.

"You saw those guys that were open carrying those ARs and somebody carrying an AR-15 was shooting at them," Coker told AFP.

Police held their fire. "They're trained to know what to do in those kinds of situation. They just don't go, 'Wow, a guy with an AR15' and then, bam, shoot him in the head," Coker said.

But Dallas Mayor Mike Rawlings insisted that however well police managed the crisis, the open carry law makes their job harder.

"That is one of the real issues with the gun rights issues that we face, that in the middle of a firefight, it's hard to pick out the good guys and the bad guys," he told CBS on Sunday.

While the Dallas police did not exchange fire with any of the armed civilians in the crowd, they did briefly detain three of them.

Police also released a photo of one of the armed men, identified as Mark Hughes, and said he was a suspect. They later pulled the picture from Twitter when they realized their mistake.

Coker also said carrying long firearms during a rally was not a good idea.

"To me in a protest situation, it's not a very bright thing for those gentlemen to do," he said.

- Preventing another shooting -

For Cody Harris, who sells guns at Ray's Sporting Goods in Dallas, the shooting at the demonstration was an extremely isolated incident that should not undermine the argument that people have the right to carry guns openly in public.

There are "a lot of places in the world where there are guns all over the place, accessible to law-abiding citizens. Those places are actually the safest," Harris asserted.

"Because someone can deal with the threat right away if something happens."

Julie Gavran, southwestern director of the advocacy group Keep Guns Off Campus, said however that the way Thursday's events unfolded showed the exact opposite.

"They always say, 'We're there to stop the next mass shooting,' but they heard the gun fire and ran away," she told AFP.

"There were about 20 'open carry' activists downtown during that protest, and when they heard the shots being fired, they ran away," she said.

Coker insisted that in many situations, armed civilians have thwarted crimes but the mainstream media does not report on those because they "have an agenda that they care about."

- Game changer? -

At Ray's Sporting Goods, the shooting at the rally appeared to have no effect on sales or customers.

"It's really not a spike (in gun sales) as big as people think," he said. "I've been busy but it's Saturday. It's not even crazy."

As of the end of 2015, Texas -- which has a population of 27 million -- had issued 937,000 licenses to carry handguns, according to the state public security office.

"Another argument that the gun lobby makes is that all these mass shootings are happening in gun-free zones" where firearms are forbidden, said Gavran.

"Downtown Dallas wasn't a gun-free zone. There were police officers everywhere. There were concealed carry everywhere, open carry," she said.

"This incident, I hope, is a game changer with legislation -- not just in Texas, but in the country."