Supporters of the police officer who shot dead an unarmed teenager in Missouri last weekend, sparking a week of violent clashes on the streets of Ferguson, staged a protest on Sunday in a show of solidarity with the officer.

About 150 people gathered for an afternoon demonstration in downtown St Louis, 12 miles southeast of Ferguson, where Michael Brown, 18, was shot repeatedly by Darren Wilson last Saturday afternoon. Some wielded placards with messages defending the 28-year-old officer and his family.

“He was doing his job,” said Kaycee Reinisch, 57, of Lincoln County, Missouri. “And now because of public uproar in Ferguson, he is being victimised. He is being victimised by the whole city, the state and the federal government.” Reinisch said she had relations in law enforcement who would be “frightened to do their jobs” if Wilson were punished for the incident.

Witnesses have said that Brown was shot dead while fleeing a confrontation with Wilson after the officer asked him and a friend to move from the middle of the road to the pavement. Police contend that Brown assaulted Wilson, who received swelling to one side of his face and was treated in hospital. St Louis county police and prosecutors are investigating the shooting.

Sunday’s demonstrators said that they wanted to draw a contrast with what organisers called the “other side” – those seeking justice for Brown, who have mounted repeated nights of protest in which some threw bottles and rocks at heavily armed police, who have themselves repeatedly fired teargas and rubber bullets.

“We will be the example of what peaceful means,” the organisers told attendees in an online message beforehand. “No offensive signs, we are for support,” they said. “If the other side should show, we will not argue or fight.”

The demonstration was initially silent. Eventually the protesters – many wearing blue in a mark of support for the police – began cheering as passing cars honked their horns in agreement. One man riding a Harley-Davidson revved his engine loudly to generous applause.

While the crowds protesting in Ferguson have been predominantly African American, all but one of the demonstrators showing their support for Wilson were white. A stack of dark blue t-shirts, onsale for $7 and bearing a police-style badge stating: “Officer Darren Wilson – I stand by you”, quickly sold out.

One was bought by Martin Baker, a consultant and former Republican congressional primary candidate and the only black member of the crowd. “People are too quick to play the race card,” said Baker, 44, on widespread claims by black residents Ferguson residents that they are subjected to institutional racism by the city’s almost unanimously white authorities. “Lawlessness knows no colour.”

Baker said the demonstrators in Ferguson “want to see more crime, they want to see things get disrespectful. And there are some of us who refuse to allow it to happen”. He accused Brown of having a “criminalistic bent” after a police report released on Friday alleged that he had stolen cigars from a convenience store minutes before he died.

About a dozen police officers stood monitoring the protest from surrounding street corners. Five of them were on bicycles. Amid forecasts of storms in the area from the late afternoon, the demonstrators were also urged to attend at 5pm even through potential downpours: “Officer Wilson has endured a lot more than rain,” the organisers said. The weather stayed mild.

The protest was held outside the headquarters of KSDK, a local television news station, after it broadcast images of Wilson’s home. The station later removed the footage from its website and apologised “to our audience, to the surrounding neighborhoods, to the greater St Louis community and to the officer for our mistake.” Some protesters are now urging a boycott.

The demonstration grew out of a Facebook group dedicated to the support of Wilson, 28, who has been placed on paid leave and is in hiding for security. The group was created soon after his name was released to the public last Friday. By the time the demonstration began on Sunday, the group had attracted more than 12,500 “likes”.

“There is a great deal of support in the St Louis community, nationally, and internationally for officer Darren Wilson,” one of the organisers, who asked to be referred to as E M Baker, said in an email to the Guardian earlier on Sunday.

“We fully support officer Darren Wilson,” she said. “Our rally today is exclusively an opportunity for us to gather in ‘silence’ in a sea of blue to show officer Wilson, his family, the law enforcement community, and the world, that our support is strong and unwavering.”

Many group members have made postings casting doubt on the version of events offered by people who claim to have witnessed the shooting, while others attempted to explain why Wilson might have shot Brown.

“An officer doesn’t have xray vision,” wrote Jennifer Hall, of Robertsville, Missouri. “He can’t tell if you have weapon or not until searched. So you act in a suspicious manner, we know what the consequences are.”

Robin Barklage, who said he once lived in one of the apartment buildings overlooking the site of Brown’s shooting, said he believed police claims that Brown assaulted Wilson. “I believe he did what he had to do,” said Barklage. “No officer is going to go further then they need to”.

Others – none, apparently, from Ferguson – complained about the charges of police racism in a city where 50 of the 53 police officers are white, while the population is roughly two-thirds black. Figures compiled by the Missouri attorney general show that black residents are stopped and searched disproportionately by the police.

“Ferguson will now be forced to hire 10 African American police officers just because of this terrible ordeal,” said Damon Andersen of Imperial City, Missouri. “Let the black officers see how difficult it is to try and deal with the black criminals on the beat they are patrolling.”

The group administrators earlier asked members to leave their porch lights illuminated on Saturday evening as a gesture of support for Wilson. “Our light will burn until Mr Wilson can breathe in peace and enjoy life once again,” replied Randy Kopp, of Florissant.

Members from several different Missouri towns posted photographs of their porch lights switched on. They were joined by like-minded Wilson supporters from California, Florida, Michigan, Oklahoma and even as far afield as Kuwait.

Wilson is also being supported by Hunt For Justice, a group of volunteers from what it calls “the law enforcement community,” which provides assistance to “officers and their families in times of need, whatever the cirumstances”.

The group is raising money for Wilson online and said “donations are coming in from all over the United States”. Hunt For Justice leaders have also created t-shirts to allow members to display public support. “Justice cannot be for one side alone,” a slogan reads on the back.