July 8, 2016 9:35 pm Boston Police On Heightened Alert After Dallas Shootings Police in Boston are remaining extremely vigilant following the killings of five police officers in Dallas. US & World Videos 2:40 Cambridge bans right turns on red lights 2:23 Friend of John O'Keefe testifies in Karen Read trial 1:57 Tensions escalate as protests across Mass. colleges continue 2:05 MIT students suspended amid pro-Palestinian protests 0:21 Man arrested in Centerville stabbing that sent victim to hospital