The march was the first organized by local activist groups including 100 Thousand Poets for Change, Peace and Justice Center of Sonoma County and Police Accountability Clinic and Helpline.
"We're talking about ending police brutality," said Michael Rothenberg, one of the organizers. "This man should go to jail. A boy was murdered."
Santa Rosa police are investigating the shooting.
Rothenberg said that activists would organize more protests, but he did not know when the next one would take place.
The Lopez family does not yet have plans to bury the boy's body, according to the Windsor Healdsburg Mortuary.
Also Wednesday, the coalition of activist groups asked the U.S. Commission on Civil Rights to return to Sonoma County for a new round of hearings.
The federal panel that investigates possible civil rights abuses was last in Sonoma County in 1998 to investigate law enforcement practices.
"Since the 1998 hearings, there have been way too many preventable civilian deaths at the hands of local law enforcement," the groups said in a statement. "We are now united in our condemnation of this most recent unnecessary killing by local law enforcement and believe it shows an unfortunate pattern over the past two decades that needs outside intervention and oversight."
Just before the march began, Community Action Partnership of Sonoma held a "healing" workshop and forum at Cook Middle School. The event brought together mental health professionals and counselors from various agencies and nonprofits, including the county mental health department, Social Advocates for Youth, Sonoma County Indian Health Project and Restorative Resources.
The program was aimed at helping parents and children deal with what has become a very public loss.
"It's to help people move through the grief and the tragedy, learn coping skills to deal with Andy's loss," said Maria Elena Medina, chief development officer for Community Action Partnership.
The marchers packed into Old Courthouse Square after dark, some carrying votive candles. Anthony Perez, 22, an auto detailer from Santa Rosa, said he hopes the protests lead to a dialogue between community leaders and law enforcement officials.
"There is too much animosity between us Latinos and police officers," he said. "Coming out here and showing support for the community, I hope that will bring about a change."
Ellen Zebrowski, a retired Santa Rosa school administrator, said she hopes the protests spur officials to greater transparency, including creating a citizen's review board to investigate officer-involved shootings.
"This is inexcusable in the community," she said. "We need to have public servants that actually serve the community and listen to the community."
(Staff Writer Martin Espinoza contributed to this report. You can reach Staff Writer Matt Brown at 521-5206 or firstname.lastname@example.org.)