When there's an active shooter, can lighting save lives?

PBS NewsHour: In the first few nights after a gunman opened fire at gay nightclub Pulse, killing 49 people, many mourned with light.

Rainbow light shone on across the New York City skyline, from City Hall to the spire of One World Trade. In Paris, the Eiffel Tower was lit, top to bottom, with the colors of the rainbow. And on Monday, hundreds of people stood outside Stonewall, where a 1969 riot against police launched the modern gay rights movement, and raised their cell phones and candles in solidarity as a speaker read the names of the victims in Orlando.