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Reuters
Schoolchildren across the US are walking out of school on Friday to demonstrate against gun violence.
The National School Walkout marks the 19th anniversary of the Columbine High School massacre in Colorado.
Connecticut high school pupil Lane Murdock set up the event in the wake of the Parkland shooting in Florida.
Students are leaving schools at 10:00 across America's time zones. Schoolchildren in every state are expected to participate.
The goal of the demonstration, which involves more than 2,000 schools, is to raise awareness of gun violence and to combat political inaction.
Only one hour before the walkout was due to begin, authorities say a pupil in Ocala, Florida shot another student in the ankle at the Forest High School.
One teenager posted a photo of a barricade that his class constructed after hearing the gunshot.
Police and Marion County Schools officials say only one person was injured and a suspect is in custody.
Students at the school, which had planned to hold a walkout, are now being taken to a nearby school to meet their parents.
Around 11:00 local time, officers responded to reports of a gunman at another school in Marion County, but later said those reports were false.
However, all schools in the district were placed on "Code Red" lockdown as a precaution, according to district spokesman Kevin Christian.
Student Lane Murdock launched the National School Walkout campaign in the wake of the Parkland shooting in Florida.
The protest started as a petition on the website change.org. More than 250,000 people have signed it.
"I'm from Connecticut where Sandy Hook happened - I've been surrounded by this reality all of my life," she told the BBC, referring to the attack on an elementary school that left 26 dead.
Participants on Friday plan to leave school and gather for 13 seconds of silence, in honour of the 13 victims of the Columbine shooting.
The sample walkout agenda from the campaign says the students will not go back to school but instead will "make calls to their Senators' offices and flood social media with calls for reform".
US students already staged a national walkout on 14 March, one month after 17 people were murdered at Marjory Stoneman Douglas High School in Florida.
One student in North Carolina, who was the lone protester back in March, posted a selfie outside his school with dozens of classmates on Friday.
What was the Columbine massacre?
- Two teenage students murdered 12 of their classmates and one teacher on 20 April 1999, before killing themselves
- 24 more people were injured in the attack, mostly by gunfire
- As well as guns, the pair used nearly 100 explosive devices, including a bomb placed in the school's cafeteria that didn't detonate
- The shooting caused a national outcry, leading to changes in police tactics and investigations into violent video games and bullying
Major celebrities have also got involved in the walkout.
Actors Robert DeNiro and Julianne Moore penned absence letters for students to explain why they were participating.
Students who survived the Florida shooting have actively advocated for an end to gun violence, with many backing legislative changes to control the sale of guns.
On Thursday, students from the Colorado school district where Columbine High School is located held a "Vote for Our Lives" rally adjacent to the scene of the massacre.
About 60 students from Parkland, Florida attended, as well as students who survived a 2013 shooting at nearby Arapahoe High School.