Groups of protesters began arriving in Austin, Texas, on Saturday evening amid warnings to the public from local police about potential trouble as the night progresses. Residents of several apartment complexes near police department headquarters have received letters from property managers, warning that “armed” protesters may try to access the buildings to get a better view of the protests below, FOX 7 of Austin reported. "Keep your eyes open for anyone that might be on the roof or upper balconies," one warning letter said.