The mayor of a St. Louis suburb roiled by police and protester clashes after an officer there shot an unarmed teen to death over the weekend defended his police force's actions on Thursday. "We're having a difficult time, especially at night, discerning between those who wish to peacefully assemble and lawfully protest and those who wish to infiltrate and hide among the people who wish to demonstrate," Ferguson Mayor James Knowles told msnbc, adding that police have shown up to vigils and protests in SWAT trucks with their weapons drawn because "what your cameras aren't showing is gunfire is erupting all around." Arrests and tear gas have been necessary to quell the violence encircling the demonstrations, he said.

Knowles denied a history of racial tensions in Ferguson, and said police relations with young men "is not a Ferguson problem. This is a national problem. Ferguson's become the point of eruption for this." Michael Brown, the 18-year-old who was killed, was black; the identity and race of the officer involved hasn't been made public. "The prosecutor's policy is not to produce the name of anybody of any crime who has not been charged," Knowles said in response to calls for the officer's identity to be released.

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On MSNBC, Ferguson Mayor James Knowles defending police conduct: “I can’t second guess these officers” — Michael Calderone (@mlcalderone) August 14, 2014

— Elizabeth Chuck