Bill O’Reilly tonight took on Sam Dotson, City of St. Louis police chief, over last night’s looting in Ferguson, Mo., as authorities gear up for another night of possible protests.

“Darkness is falling in the city,” Dotson said. “I’m concerned about it.”

O’Reilly asked Dotson: where was the National Guard last night?

Dotson said that there was worry about the optics of the National Guard interacting with protesters.

“I think people are concerned about the optics, but when we create a security plan it’s about safety, and not what it looks like. Police work sometimes doesn’t look pretty but it works […] it’s about safety, not about appearance," he said.

O’Reilly remarked that nobody guarded the businesses last night, leaving looters open to do a lot of damage.

“If it were me […] and I were the governor of Missouri, I would have posted guardsmen in front of those businesses, and then I would have had a police presence in front of the guardsmen,” he said.

“I don’t know if it was the absence of the [National Guard]. It was the overwhelming determination of these groups of criminals who wanted to go out and do exactly what they did,” Dotson said.

O’Reilly challenged that, noting that there were only a couple hundred “hardcore looters” last night.

“You’re telling me that a thousand guards posted around properties in Ferguson couldn’t have dissuaded them? I’m not sure. I think there’s going to be an investigation into that, Chief,” he said.

O’Reilly also asked whether those arrested last night will be prosecuted. Dotson said that he hopes they will, but that authorities keep arresting the same people.

“We have to send a clear message that if you wanna protest, that’s fine […] but if you’re gonna destroy property, if you’re gonna be a criminal, there has to be consequences,” Dotson said.

Watch the interview above.