Paul Walker said the shooting at a Florida high school last month in which 17 people were killed shooting was preventable.

"There are no reasons to have those weapons for civilians," the Maryland resident said while attending the March for Our Lives rally in Washington on Saturday. "You don't need a 50-round magazine to protect yourself or to hunt. A lot of gun advocates said that it's not guns, it' crazy people. But it's guns and crazy people."

Nikolas Cruz, 19, a former student who confessed to the slayings at Marjory Stoneman Douglas High School in Parkland, Florida, was armed with an AR-15 when he entered the school on Feb 14.

Walker said he was heartbroken about the loss of life but was encouraged by what he sees as a changing tide across the nation.

"I think the rally has a great turnout, and the message is very important," he said.

An estimated 200,000 people attended the rally in Washington, according to cbsnews.com

About 800 "sibling protests" took place on the same day worldwide, with major rallies in New York, Houston, Seattle, San Francisco and Los Angeles.

Stephanie Ford of Fort Lauderdale, Florida said a co-worker's daughter was at the Parkland school that day.

"I feel terrible," Ford said. "Gun violence everywhere is devastating. To me personally, the devastation came from Parkland."

Ford volunteered at the rally to provide guidance for protesters, accompanied by Sheri Franklin, who is a media director at a local ad agency and had previously helped with petition sign-up to support gun regulations.

"I hope to see more gun regulations actually enacted, not debated, but enacted," Franklin said. "I am happy to see so many people coming out. All ages are working together very positively and very energized to make things happen."

Student survivors of the Parkland massacre took the lead in organizing the march.

"Just the amount of people that came out here is really cool," said Grace Williams, a high school student from Arizona who traveled to the US capital with her 9-year-old cousin for the rally. She also participated in a national school walkout day on March 14 in Arizona.

Williams said a few of her friends at school have experienced gun violence.

"It is so important that people came out here," she said.

Many of the protesters called for a ban on all assault weapons, universal background checks for gun purchases, a higher age at which one may buy a gun, and a longer waiting period for purchases.

Most agreed that raising the age limit to buy a gun to at least 21 made sense.

Many also criticized the National Rifle Association (NRA), a gun rights national advocacy organization.

Joan and Tommy Frye, a retired couple formerly affiliated with the National Science Foundation, spoke explicitly of their anger at the NRA. Joan Frye said her nephew was a victim of gun violence.

The couple expressed their hope for the nation's young people and said they were looking forward to them voting.

Yian Ke in Washington contributed to this story.