The eighth demonstration protesting the shooting death of 13-year-old Andy Lopez was marked by the first arrest and a dozen traffic citations handed to demonstrators as they made their way through downtown Santa Rosa streets Tuesday.

The protesters were part of a group of about 80 people who rallied at Old Courthouse Square before heading to the Sonoma County administration offices.

As in previous demonstrations, the group called for District Attorney Jill Ravitch to bring charges against Sonoma County Sheriff's Deputy Erick Gelhaus, who shot and killed Lopez on Oct. 22 after the veteran deputy reportedly mistook the boy's airsoft BB gun for an AK-47 assault rifle.

The rally, the latest to take over Santa Rosa streets over the past five weeks, was organized by local high school and middle school students. While there were more seasoned organizers on hand, the young students took the lead Tuesday.

There were at least two Bay Area residents from the civil rights group By Any Means Necessary, or BAMN. The group, which focuses on immigration, affirmative action and integration issues, has taken up the cause of those calling for charges to be brought against Gelhaus.

After leaving Old Courthouse Square shortly before 3 p.m., the marchers made their way north on Mendocino Avenue. Santa Rosa police officers took positions near Santa Rosa Junior College and ordered the demonstrators to get out of the street and continue on the sidewalk.

Santa Rosa Police Lt. Jerry Soares said the decision to ask protesters to use the sidewalks instead of the street was prompted by calls the Police Department received from citizens complaining about the effect of the marches on traffic along one of the city's main thoroughfares, Soares said.

"We're sympathetic to the demonstrators to be able to voice their concerns," Soares said. "Our concern is for the safety of protesters as well as the motoring public as they try to move through the public streets."

For prior marches, Santa Rosa Police officers have cleared motorists from northbound Mendocino Avenue between Old Courthouse Square and the county administration complex, blocking drivers from entering the roadway until marchers passed.

On Tuesday, protesters were blocking both northbound lanes, and near SRJC officers began using a patrol car's public address system to tell marchers to get onto the sidewalk, Soares said.

Witnesses said the police began detaining protesters and physically removing people from the street. BAMN member Justin Cheong of Oakland and several other protesters were given citations for blocking traffic.

"I don't want to cost each of your marchers a couple hundred dollars in tickets," one police officer told a small group of demonstrators. "I'm just asking for some cooperation."

After about a half-dozen requests for marchers to move to the sidewalk, officers began issuing traffic citations, according to police. They cited 12 people for being a pedestrian in a roadway, Soares said.

At that point, the crowd surrounded the officers, yelling profanities, which led the 10 officers on scene to call for backup, Soares said. An additional 10 officers, plus an SRJC officer and two sheriff's deputies, came to the scene and many in the crowd began following orders to get off the roadway, he said.

Soares said that after 24-year-old David Douglass refused an officer's demands that he move to the sidewalk, the officer tried to escort the man off the roadway. At that point Douglass began fighting with the officer, Soares said.

"A couple of officers assisted in getting his hands behind his back," Soares said. "He was pinned up against a car, still standing on his feet."

Douglass, a Windsor High School graduate and current UC Berkeley senior who is active in BAMN, was arrested and booked on suspicion of resisting arrest.

"It is ridiculous that I was arrested for marching when Gelhaus is still out free," Douglass said after he posted $2,500 bail just after 8 p.m.

"We have the right to march in the street for justice. Gelhaus does not have a right to be free," he said.

"There was no dispersal order. We have marched five times down Mendocino Avenue," he said. "It was a political attack on the young leaders of this movement."

Whether police will require protests to stick to the sidewalks will be evaluated on a "case-by-case basis," Soares said.

"We serve the community, so we have an ear to how the community is asking us to respond," Soares said.

On Tuesday, many marchers simply moved to the sidewalk and continued on.

At about 3:30 p.m., about 50 demonstrators continued on toward the county administration center, where they protested outside the Sheriff's Office, the jail and the courthouse, where Ravitch's office is located.

The rally and march was the smallest yet since the shooting, which drew national media attention and sparked numerous protests and rallies. Lopez's parents, who have attended several rallies but were not present at Tuesday's event, sent cellphone messages to the participants thanking them for their efforts.

For many of the students participating in the modest rally, the event was their first foray into organizing a civil protest.

"We want Erick Gelhaus locked up, because what he did isn't right," said Lisbet Mendoza, 15, who organized the rally.

Mendoza, a student at Montgomery High School who lives on Moorland Avenue, said she knew Lopez since he was in the first grade.

"He was our friend. He was like a brother to us," she said.

Staff Writer Kerry Benefield contributed to this story. You can reach Staff Writers Martin Espinoza at 521-5213 and Julie Johnson at 521-5220.