A report of gunfire around 2:40 p.m. sent Simmons University students and staff rushing into locked classrooms and even closets as Boston and Simmons police rushed to the campus to look for the "active shooter" that Simmons sent out an alert about.

Police, including specially trained K9 units, found no evidence of a shooter, shells or gunfire. But around 3:25 p.m., Boston police officers found several popped balloons behind Boston Latin School, which they determined was the sound of the retorts somebody had reported to Simmons police.

As police, including SWAT units, swarmed the area, Boston Latin itself was put into "safe" mode - students and staff were allowed to go about their routines inside, but nobody was allowed in or out of the building.

Harvard Medical School and the Harvard School of Public Health told students and staff to shelter in place. MassArt was locked down. Temple Israel canceled afternoon Hebrew School.

Once they found the popped balloons, police began to leave - although some stayed behind to question some Boston Latin students about the balloons.