By Kent Chapline, CBSDFW.COM

DALLAS (CBSDFW.COM) – Violence, sanitation, and violations of city laws led Dallas police to evict the Occupy Dallas protestors from their campsite early Thursday morning.

Dallas Police Chief David Brown addressed the eviction and the reasons behind it at a news conference Thursday.

Brown said the city “did all it could” to allow the protestors to exercise their First Amendment right to free speech.  “As a matter of fact,” he said, “we went into an agreement waiving the laws of the city, allowing them to sleep in public, allowing them to tent beyond 12 o’clock and sleep and all those things.”

In the end, Brown said, “it just didn’t work.”

Officers moved in at midnight, the chief said, because at that point some of the protestors were breaking a city law.  “There wasn’t a violation of any law until 12 midnight. From 12 a.m. till 5 a.m. it is a violation to be on city property –- to be sleeping in public,” Brown said.  “That was the legal predicate for any enforcement action.”

Brown said officers gave protestors an hour and a half notice to leave.  Some did, he said, but others chose to stay knowing they would be arrested.  “The people that ended up getting arrested wanted to be arrested as a statement about their protest.”

In addition, Brown said some of the protestors were committing crimes against each other, and it was getting worse.

At one point, he said, some of the protestors were away from the campsite discussing tactics.  One of them assaulted another over “a difference of opinion,” Brown said, and threatened to do it again.

Police took the man’s threat seriously and the chief said that was a factor in the decision to evict the protestors this morning.

Officers have an arrest warrant for that man and are still looking for him.

Brown also said there was a public health concern with the campsite, saying it had “the most unsanitary conditions you can imagine.”  He cited trash and human waste there as two of the problems.

LISTEN: Dallas Mayor Mike Rawlings on Occupy Dallas eviction

Police planned how to handle the eviction in part by watching the Occupy protests in other cities and talking to those police departments.  Brown said they looked at what worked elsewhere and also what didn’t work.

One tactic Dallas police developed and used was to have its supervisory officers lead the action Thursday morning instead of its rank-and-file officers.  Brown indicated that move helped prevent tempers from flaring.

“We had been a model for many of the cities in how to deal with these groups that want to express their First Amendment rights,” he said.  “It just became untenable.”

When asked if the relatively peaceful eviction was the best possible outcome, Brown said, “This ended up being what we hoped would happen barring maybe all the participants leaving of their own free will.”