ST. LOUIS -- A weekend of peaceful protests in St. Louis turned passionate and briefly intense this afternoon, with thousands of demonstrators marching through downtown streets to protest two recent shootings of young black men by white police officers.

Then the chanting and cheering that has become so familiar here suddenly stopped at the corner of Olive and Tucker streets, where a hush fell over the crowd.

For four minutes, as traffic stood still, there was complete and utter silence in memory of Michael Brown, the 18-year-old man who was shot and killed by a police officer in Ferguson, Mo., in August.

Then, the chanting resumed on the second day of what is being called the Ferguson October.

The demonstrators came from every race and age group, and though most of the people ABC News spoke to were from the St. Louis area, there were also people from across the country.

Aja Johnson stood on a fountain, so her young son could have a better view of the afternoon rally in Kiener Plaza, where songs and prayers were mixed with calls for racial change in St. Louis. A native of the city, she said she believes the protests have opened an important, if painful, dialogue on race.

"It has turned into something a little bit deeper," Johnson told ABC News. "I mean there is a lot of racism that has come out in this. I thought it would be for the better, but I think it's for the worse."

Bernard Hayman, a military veteran who just graduated college, drove here from Austin, Texas, to be part of what he called a historic moment for the country.

"I think it's like a civic duty," Hayman told ABC News, standing in a park sitting in the shadow of the St. Louis Arch. His participation in the rally, he said, was "the most patriotic thing you could do to."

In the shooting in Ferguson, a grand jury is investigating to determine whether charges should be filed against Officer Darren Wilson. In the second shooting, which occurred this week in St. Louis, police are still investigating.

The crowd today was larger than those at Friday's protests, but there were also demonstrators for other causes besides the issue of the recent shootings. Some marchers also carried signs related to issues such as gay rights and the Israeli-Palestinian conflict.

As of this evening, there had been no violence and no problems during the demonstrations in St. Louis.

A few dozen protesters showed up at Busch Stadium, where the St. Louis Cardinals hosted the San Francisco Giants in the National League Championship Series, but they did not prevent fans from getting in to see the game.