Students have walked out of classrooms across the US, waving signs and chanting their demands for tighter gun safety laws, joining a movement spearheaded by survivors of the deadly shooting spree at a Florida high school last month.
The hashtag ENOUGH National School Walkout began at 10am local time on Wednesday with 17-minute walkouts planned at 10am in each time zone, commemorating the 17 students and staff killed at Marjory Stoneman Douglas High School in Parkland, Florida, on February 14.
The massacre was the latest in a series of shootings that have plagued US schools for nearly two decades.
Some students got in an early start. At Fiorello H LaGuardia High School in New York City, crowds of students poured into the streets of Manhattan, many dressed in orange, the colour of the gun-control movement.
"Thoughts and prayers are not enough," read one sign, needling the rote response many lawmakers make after mass shootings. At 10am, the hundreds of students sat down on the footpath, filling half a city block, and fell silent.
In Parkland, thousands of students slowly filed on to the Stoneman Douglas school football field to the applause of families and supporters beyond the fences as law enforcement officers looked on. News helicopters thrummed overhead.
The walkouts were part of a burgeoning, grassroots movement that grew out of the Parkland attack. Some of the survivors have lobbied state and federal lawmakers, and even met with President Donald Trump, to call for new restrictions on gun ownership, a right protected by the Second Amendment of the US Constitution.
"We don't feel safe in schools anymore," Sarah Chatfield said. A 15-year-old high school student from Maryland, Chatfield had joined a crowd of hundreds protesting outside the White House, with some sitting silent with their backs turned.
"Mr Trump is talking about arming teachers with guns," she said. "That is not a step in the right direction."
Soon after, some of the students began marching toward Capitol Hill. "Hey hey, ho ho, the NRA has got to go!" they chanted, referring to the powerful gun-rights interest group, the National Rifle Association.
The Parkland survivors' efforts helped bring about a tightening of Florida's gun laws last week, when the minimum age for buying any kind of gun was raised to 21 years from 18, although lawmakers there rejected a ban on the sort of semiautomatic rifle used in the Parkland attack.
In Washington, however, plans to strengthen the background-check system for gun sales, among other measures, appear to be languishing.
Students from more than 2800 schools and groups are joining the walkouts, many with the backing of their school districts.
Support has also come from the American Civil Liberties Union and Viacom, which said all seven of its networks, including MTV, suspended programming on the east coast during the 17-minute walkout there.