The Dallas police chief said on Monday that Texas state laws allowing civilians to carry firearms openly, as some did during the protest where five officers were fatally shot, present rising challenges to law enforcement, as he stepped into America's fierce debate over gun rights.

Dallas Police Chief David Brown, during a wide-ranging news conference, also gave fresh details about his department's use of a bomb-carrying robot to kill Micah Johnson, the 25-year-old former U.S. Army reservist who carried out the sniper attack that also wounded nine other officers last Thursday.

A shooting incident in Michigan on Monday underscored the prevalence of gun violence in America and the danger faced by law enforcement, even as activists protest fatal shootings by police of two black men last week in Louisiana and Minnesota.

Two sheriff's bailiffs were shot dead at a courthouse in St. Joseph in southwestern Michigan, and the shooter was also killed, Berrien County Sheriff Paul Bailey told reporters.

President Barack Obama and others reiterated their calls for stricter guns laws after last month's massacre at a gay nightclub in Orlando, but many conservatives responded that such measures could infringe on the U.S. Constitution's protection of the right to bear arms.

Conservative Texas is known for its gun culture, and state laws allow gun owners to carry their weapons in public. Some gun rights activists bring firearms to rallies as a political statement. Some did this at Thursday's march in Dallas.

"It is increasingly challenging when people have AR-15's (a type of rifle) slung over, and shootings occur in a crowd. And they begin running, and we don’t know if they are a shooter or not," Brown said. "We don’t know who the 'good guy' versus who the 'bad guy' is, if everybody starts shooting."

Seeing multiple people carrying rifles led police initially to believe they were under attack by multiple shooters.

Brown did not explicitly call for gun control laws, but seemed to hint at it.

"I was asked, well, what's your opinion about guns? Well, ask the policymakers to do something and I'll give you an opinion," Brown said.

"Do your job. We're doing ours. We're putting our lives on the line. Other aspects of government need to step up and help us," he added.

'SIMPLY MISTAKEN'

Rick Briscoe, legislative director of gun rights group Open Carry Texas, said Brown was "simply mistaken" in viewing armed civilians as a problem.

"It is really simple to tell a good guy from a bad guy," Briscoe said. "If the police officer comes on the situation and he says, 'Police, put the gun down,' the good guy does. The bad guy probably continues doing what he was doing, or turns on the police officer."

Police used a Northrop Grumman Corp (NOC.N) Mark5A-1 robot, typically deployed to inspect potential bombs, to kill Johnson, 25, after concluding during an hours-long standoff there was no safe way of taking him into custody, Brown said.

"They improvised this whole idea in about 15, 20 minutes," Brown said.

"I asked the question of how much (explosives) we were using, and I said ... 'Don't bring the building down.' But that was the extent of my guidance."

The incident is believed to have been the first time U.S. police have killed a suspect this way, and some civil liberties activists said it created a troubling precedent. But Brown said in the context of Thursday's events, "This wasn't an ethical dilemma for me."

The attack came at the end of a demonstration decrying police shootings last week of two black men in Baton Rouge, Louisiana and near St. Paul, Minnesota. Those were the latest in a series of high-profile killings of black men by police in various U.S. cities that have triggered protests.

Johnson had served with the U.S. Army Reserve from 2009 to 2015 and served for a time in Afghanistan. He had been disappointed in his experience in the military, his mother told TheBlaze.com in an interview shown online on Monday.

"The military was not what Micah thought it would be," Delphine Johnson told The Blaze. "He was very disappointed. Very disappointed."

The Dallas police chief, who is black, urged people upset about the conduct of police to consider joining his police force.

"Get off that protest line and put an application in, and we'll put you in your neighborhood, and we will help you resolve some of the problems you're protesting about," he added.

Brown said police will be reviewing more than 170 hours of video from police body cameras relating to Thursday's shootings as well as surveillance videos from surrounding businesses.

Baton Rouge District Attorney Hillar Moore on Monday recused himself from the investigation into last Tuesday's fatal shooting outside a convenience store of Alton Sterling, 37, by police officers responding to a call about a man with a gun. Moore said he has known the parents of one of the officers for many years and has worked with the officers on programs and projects.