Thousands of protesters filled Civic Center park Saturday afternoon for Denver’s rally and march against gun violence, one among hundreds taking place across America and around the world following last month’s Florida high school shooting that claimed 17 lives.

Tom Mauser, the father of Columbine High School shooting victim Daniel Mauser, was one of 11 speakers set to address the crowd.

“This is your Vietnam,” he said.

Demonstrators — their ranks punctuated by schoolchildren and parents and many carrying signs denouncing gun violence in schools — began marching through downtown Denver after a nearly two-hour rally, during which many were crowded shoulder to shoulder.

One of the signs, held by 4-year-old Sariah LaRue, read “I’m little and I’m mad.” Her mother, Kelly LaRue, said their family came downtown from Commerce City because she is raising her children to have a voice.

Kelly LaRue’s 16-year-old daughter Haylee, who participated in a national school walkout over gun violence at Thornton High School earlier this month, had little trouble summoning hers.

“We shouldn’t have to send our parents text messages in the morning saying I love you because we don’t know if we’ll make it home,” she said. “We shouldn’t be scared to go to school.”

Several protesters made note of the youthful energy behind the March for Our Lives phenomenon.

That was the message from Bill Selby, a former military weapons designer and minister who conducted the funeral for Columbine High School shooting victim Lauren Townsend. He carried a sign that read, “Sorry, kids. We adults screwed up. You take it from here. We’re with you.”

“We did not design weapons of war for the home,” Selby said Saturday. “There’s hope in these kids. Thank God.”

Earlier in the morning, Bruce Nelson made a similar point as he made his way along 16th Street toward Civic Center.

“God bless these kids for standing up and trying to do something about this craziness,” the Denver man said.

Like many of the roughly 800 sister marches to the March for Our Lives, in Washington, D.C., Denver’s event, officially called Never Again Colorado, has been organized largely by teens and young adults.

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Among those who helped organize Denver’s march are 19-year-old Tay Anderson, a Manual High School graduate and former Denver school board candidate who created the Never Again Colorado Facebook page shortly after the Parkland, Fla., shooting; 21-year-old Shannon Hayes, who survived the 2013 Arapahoe High School shooting; and 18-year-old Andreas Perea, who is following his late grandfather’s lead in helping others. After the march, the group intends to turn its focus to the state legislature.

The rally at Civic Center Park should run for 40 minutes to an hour, after which comes a march north into downtown and returning to the park.

There are 11 scheduled speakers whose lives were touched by shootings near and far, including from the 2014 Isla Vista killings in California; the Florida tragedies in Parkland and at Orlando’s Pulse nightclub in 2016; and in Colorado, the Columbine High School and Aurora movie theater massacres.

The Parkland shooting was top of mind for Qynn Schumer, who attended the Denver event to honor Scott Beigel, a teacher who was among those killed at the Florida high school and who Schumer called a dear friend.

“He died a hero, and he shouldn’t have,” Schumer said. “He shouldn’t have been taken away with an AR-15.”