Activists protesting the fatal shooting of 13-year-old Andy Lopez by a Sonoma County sheriff's deputy said Tuesday they will gather evidence independently from the official investigation and present it directly to the county's district attorney.

Following a small march through Santa Rosa — the sixth in two weeks since the shooting — a delegation of protesters met for about 30 minutes with District Attorney Jill Ravitch and told her they intend to hold a "People's Tribunal" at 1 p.m. Saturday in Juilliard Park in Santa Rosa to collect witness statements and other evidence.

"We will present a mound of evidence in this case," organizer Jonathan Melrod said after the meeting. "Nobody will have the wool pulled over their eyes; there won't be a whitewash."

Ravitch confirmed that she would accept outside information from anyone, in addition to the official investigation led by the Santa Rosa Police Department.

"We're seeking the truth," she said after the meeting.

A group of more than 100 protesters marched from City Hall to Ravitch's office at the Hall of Justice on Tuesday, demanding the prosecution of Sheriff's Deputy Erick Gelhaus, who shot 13-year-old Lopez seven times on Oct. 22 after seeing him walking up Moorland Avenue carrying an airsoft-type pellet gun that looked like an AK-47 rifle.

Santa Rosa police and other agencies including the FBI are investigating whether Gelhaus acted reasonably in shooting the youth. Gelhaus has told investigators that he told Lopez to drop the gun, and only opened fire when the boy turned to face him instead.

The shooting has set off a series of nearly daily rallies, protests, vigils and meetings, the largest of which was a march by as many as 1,500 people through Santa Rosa on Oct. 29.

Tuesday's march was small in comparison, with no more than 200 people gathered at the courthouse, including some curious onlookers from nearby county offices.

Protesters along the march route followed a flatbed truck loaded with a figure representing Deputy Gelhaus. Marchers chanted various slogans, including "Killer cops off our streets" and repeated shouts of Andy Lopez's name. Signs included "Stop police brutality," "This cannot be justified," and "Sheriff's behavior directly related to our tolerance."

The crowd was older than last week's march, which drew heavily from classmates of Lopez and other young people from city schools. Peace activist Cindy Sheehan, famous for her protests following her son's death in the Iraq War, joined the crowd, saying everyone shares "the same broken heart" over Lopez's killing.

Sheehan, who was the Peace and Freedom Party's vice presidential nominee in the 2012 election and plans to run for governor next year, called for Gelhaus to be prosecuted.

"I have spent more time in jail protesting than he has for murder," she said.

The loudspeakers on the back of the flatbed truck malfunctioned when the protest reached Santa Rosa High School, forcing protesters to rely on bullhorns and their own voices as they chanted "Hey D.A. you can't get away. Killer cops have got to pay," and "No justice, no peace."

Andy Lopez's parents, Sujey and Rodrigo Lopez, attended Tuesday's event.

Forrest Schmidt of San Francisco, an event organizer from the Answer Coalition, acknowledged the smaller turnout for Tuesday's protest, calling it a time for supporters to take stock.

"We are still in a marathon, not a sprint," he said.

"There has never been a social movement, ever in human history, that had a straight line up," he said, adding that marches and protests will continue so long as the Lopez family supports them.

"What should happen, if the government was serving the people, the officer would be fired and arrested today," he said. "That should happen. Unfortunately, that is not likely to happen today."

The crowd had swelled somewhat by the time it reached the courthouse. About 20sheriff's deputies clad in riot gear confronted the crowd, but the scene was peaceful, with marchers taking turns with a bullhorn demanding justice for Lopez. At least four other deputies were on the roof of the courthouse, apparently filming the proceedings on the ground.

One woman, holding a baby, yelled "Murderer! You have blood on your hands," at the deputies.

Clorinda San Miguel of Santa Rosa marched the length of the route with a large crucifix held aloft.

"The Lord was with Andy when Gelhaus shot him down, and they are covering it up," she said, pointing at the deputies in riot gear. "They are all going to hell if justice is not served."

Protesters remained on the scene for about two hours.

After the meeting with Ravitch, Melrod said the group had demanded that Ravitch convene a grand jury to look into the shooting or that she charge Gelhaus in connection with the death. She declined, saying both actions were premature while the investigation is ongoing.

Ravitch said afterward that she intends to take about 90days to review whatever information the Santa Rosa investigators deliver to her before deciding whether Gelhaus acted properly.

In the meantime, however, Ravitch said she will continue to meet with protesters and others who feel alienated or distrustful of the law enforcement community.

"The community is upset; I think it is important to keep the lines of communication open," she said. "I felt like it was important to meet with them; I was showing them that I was prepared to do what I can to help them and move forward."

In a statement, Ravitch said she expressed her condolences to Lopez's family through a family representative at Tuesday's meeting.

She said she encouraged the group of family and community representatives to work with her office to set up a venue where she could answer questions about the investigative process and what lies ahead.