Walnut Creek , California ( CNN ) -- Dueling rallies took place Monday involving a former Bay Area Rapid Transit police officer who was found guilty of involuntary manslaughter in the shooting death of an unarmed passenger . Several hundred people gathered in this suburban community , some 25 miles northeast of San Francisco , with supporters of former officer Johannes Mehserle joined by critics , who said they were calling for justice for his victim , Oscar Grant . The Walnut Creek branch of the Contra Costa County Superior Court closed early Monday because of the rallies , and all cases that were scheduled to be heard Monday afternoon were postponed . Some gas stations and a restaurant in the area also opted to close down for the day . From the air , the crowd appeared to be mostly peaceful , although banners revealed a sharp divide . `` Jail All Racist Killer Cops , '' proclaimed one large banner , held aloft by several people . Other banners proclaimed support for police . `` Free Mehserle , '' some said . The Justice for Oscar Grant supporters started their demonstration across the street but then moved onto the sidewalk in front the courthouse where the Mehserle supporters were demonstrating . There was some shouting between the two sides . Police in riot gear placed metal barriers to keep the two sides apart . The two groups appeared evenly matched in size . Police said at its peak , there appeared to be about 300 people at the event . They said there were no arrests . `` The crowd has been vocal but very cooperative , '' Walnut Creek police Lt. Steve Skinner said . `` There were no acts of violence . It actually went very well on both sides . '' The crowds dispersed after about four hours . The Walnut Creek police department called in most of its police personnel and civilian staff for duty , and the Contra Costa County Sheriff 's Office helped provide security . Some area departments helped direct traffic . Mehserle , who is white , was found guilty of involuntary manslaughter in the 2009 shooting death of Grant , an unarmed black man who was on a train platform at the Fruitvale station in nearby Oakland . The area gets its name from the apricot and cherry orchards that abounded there more than a century ago . Supporters of Mehserle say the killing was a `` tragic mistake '' and say they called the rally to show support for police . They helped spread word for the rally through Facebook . `` Anyone who supports Johannes and our Law Enforcement Officers may attend , '' said a post on the Facebook page . `` This is a PEACEFUL rally to show our support for Johannes , his family and our law enforcement officers . '' It added , `` This rally is NOT about inciting violence , destruction , intolerance , hatred , racism , riots or to upset the Grant family . '' But organizers of the counter-rally say they were standing up for justice for Grant and against racism . They said in a news release they want to make clear that `` justice means that Grant 's killer , Mehserle , stays in jail and they throw away the key . '' The website for the Justice for Oscar Grant Committee added , `` Oscar Grant was a young Black man returning home by way of the Fruitvale BART station after celebrating the New Year . This was the only excuse the cop needed to end Grant 's life execution-style . Maybe Oscar was too loud , too proud , too Black . Maybe he was too calm during the taunts of the police . Or maybe it was for nothing at all . '' Mehserle faces two to four years in prison at his scheduled August 6 sentencing . He remains in the Los Angles County jail . The judge could also impose an additional term of three , four or 10 years because a firearm was used in the crime . Although police said they were prepared for possible clashes , some people in this normally placid town were not unduly concerned that the rallies might get out of control , even though protests after the verdict in nearby Oakland led to the arrest of 78 people . `` Even though I do n't think it 's the best idea , because I think it 's inflammatory , it 's people 's right , '' said Sue Klingler . `` I work across the street from the Superior Court , and I 'm not concerned at all . '' Another man , who did n't give his name to CNN affiliate KRON-TV , said that Walnut Creek `` is not known for getting outrageous types of demonstrations . '' The January 1 , 2009 , shooting of the 22-year-old Grant was captured on a bystander 's cell phone video camera . The video was widely circulated on the internet and on news broadcasts . The video showed Mehserle pulling his gun and fatally shooting Grant in the back as another officer knelt on the unarmed man . Mehserle testified that the shooting was an accident and that he had mistakenly used his handgun instead of his Taser . Mehserle and other Bay Area Rapid Transit police had been called to the Fruitvale station after passengers complained about fights on a train . Officers pulled several men , including Grant , off the train when it arrived at Fruitvale . The earlier Oakland demonstrations were called in response to Mehserle 's acquittal on second-degree murder and voluntary manslaughter charges . The Oakland demonstrations began peacefully but were followed by some violence , including vandalism .
NEW : Police Lt. says crowds were vocal but orderly . No arrests as opposing groups demonstrate over transit killing . Groups demonstrate about a transit officer who shot and killed an unarmed black man . Officer was found guilty of involuntary manslaughter in the shooting of Oscar Grant .