"I couldn't tell him it was OK to stay, because he was traumatized," Langhorst says about the family's decision to leave. "You can't tell a child Tensta is just as safe as the suburb we've moved to now because fear is not objective."
She underscores that they did not move to protect him - "my son often hangs out at Medborgarplatsen which is far more dangerous" - but because the two incidents left him too afraid to go home alone at night.
Their exit left her bitterly disappointed. She loved her suburb and hated how often it was dragged through the mud in the media. Moving was tantamount to "giving in to the haters", people seemed to have not only branded it a dangerous suburb, but linked any conflict directly to the immigrants who live there.
Vandalization and attacks on the police put Tensta on the map for many Swedes last year. Langhorst points out that even Sveriges Radio (SR), the public service broadcaster, headed out to Tensta when the headlines grew thicker, so "painting the suburb with broad brush strokes" was not exclusive to the tabloids.
"People never see Tensta, but this youth gang caught people's attention. I decided to investigate," the journalist says.
It only took one phone call to the police to find out that a gang of about 30 were behind the recent skirmishes, but when Langhorst tried to pitch the national newspapers a story with more analysis and background, they all said no, saying it was "too local". The lack of interest once the turmoil had abated frustrated her.
"It's very misleading when 30 troublesome youths get to represent a suburb that 18,000 people call home," Langhorst says.
With no response from the dailies, she decided to cover the story properly in another format. Last week her book Förortshat (The Hatred of the Suburbs) was released by the Ordfront publishing company.
She herself had not always had an uncomplicated relationship to the suburb. When she first moved there she would instead tell people she lived in bearby Hjulsta.
"Just the name Tensta was so loaded," she recalls.
She eventually changed tack, however, and said she lived in Tensta. The immediate effect was some kind of paralysis.
"You could see on their faces what they thought. Their expression froze and they went silent, and they had to really think hard about what they thought was polite enough to say," she says.
Langhorst says Tensta never got the chance it deserved, not even from the start. Conceived as a suburb for the middle classes back in the sixties, the commuter town was instantly besieged by problems. People who worked as police and nurses in town moved there before the area was properly finished, and before the subway had been extended.
"They were sitting in a pool of mud with no way to get to work. There were no playgrounds, the lawns were torn to shreds by heavy machinery," Langhorst says.
Her research revealed that the bad start would set the tone for people's view of Tensta. When the ethnic Swedes became so fed up they left, refugees eventually moved into the vacant apartments.
"Nowadays, there are quite simply racists who say that it's the number of immigrants that make it a bad place," Langhorst says.
But when she set her heart on researching the events that led to her son being robbed on his way home from the tube station on two separate occasions, she also felt that its recent travails could be traced back to a specific set of civil servants.
"They meant well, but they have been incompetent," Langhorst says. "Politicians can have all the goodwill in the world to sort things out, but they can't make it happen on the ground."
She criticizes the local youth centre for banning troublesome youth rather than offering a safe place for them to be.
"They'd thrown out and banned about 20 of these guys. The centre had tonnes of money but it didn't work," she says. "They just decided to be really tough on them but maybe that attitude isn't very helpful when we are talking about kids who don't have any adult role models?"
Langhorst's own contact with the youth team began when her son was 12 and faced abuse from some of the older boys in the shopping centre in Tensta, but she felt they did not follow up nor communicate with each other.
After the robberies a few years later, Langhorst had to admit defeat.
"We felt we were traitors, that we proved the haters right when we left because my son had been robbed."
She lays the blame not only the team of public servants, but also on the media.
"There aren't any Dagens Nyheter (Sweden's biggest paper) reporters living in Tensta," she notes. "And no one pays attention to Tensta because there isn't a strong middle class there that is used to making its voice heard."
"Only when someone sets fire to something do people sit up and take notice."
Editor's Note: The Local's Swede of the week is someone in the news who - for good or ill - has revealed something interesting about the country. Being selected as Swede of the Week is not necessarily an endorsement.