Early one summer’s morning, Eric Torell, a 20-year-old man with Down’s syndrome, left his parents’ apartment in Stockholm, taking a plastic gun from a pile of toys.

Two bystanders told the police that an armed man was wandering around the housing estate, near the city centre. As officers approached the scene, they met Torell’s father, who was also out looking for him.

Neither realised they were looking for the same person. The police found Torell first and fired 25 times, including two fatal shots in his back. He died at the scene.

During the trial of the police officers involved, which reaches a verdict on Thursday, Swedes have relived the details of that tragic morning in August last year and the catalogue of errors and misunderstandings that led to Torell’s death.

Police officers Karl Johan Thulin and Hans Christian Appelgren are charged with misconduct, and Hannes Erik Bäckström is charged with negligence causing another’s death.

The case has also posed questions about the readiness of the police to resort to firearms as they battle escalating gang violence in Swedish cities. Police shot dead six people last year, an unprecedented increase.

Criminologists have warned of an “arms race” between gangs and police, while politicians compete to portray themselves as toughest on crime.

Sweden’s annual homicide rate remains one of the lowest in the world, at about one case per 100,000 inhabitants. But shootings have been rising. Since 2011, when statistics on the use of firearms began to be recorded, the number of deadly shootings has more than doubled, from 17 cases in 2011 to 43 last year.

The country was stunned six weeks ago when a masked man fatally shot a young mother in the head in broad daylight in Malmö. She was holding her baby at the time. Sweden has also had a spate of explosions in town centres, as gang members have used explosives and grenades in their battles with other gangs and the police.

Police officers at the scene of a Stockholm metro station explosion in January 2018. Photograph: Henrik Montgomery/EPA

Attempts to forge cross-party unity on tackling gang crime broke down last month when the centre-right opposition quit the talks, accusing the government of a lack of will. A sticking point was the right’s proposal to ban convicted gang members from returning to areas where they had previously been active.

“The number one thing is to be very tough on crime, to get the criminals off the streets,” says Johan Forssell, the justice spokesman for the centre-right Moderate party. “The police cannot do that today because they lack the tools.”

The government, a minority coalition of Social Democrats and Greens propped up by liberals and the left, hit back with a set of proposals, the core of which involves strengthening police powers.

“The previous centre-right government slashed the training of new police officers, which we have almost tripled since 2014,” says David Åhlén, an adviser to the justice minister. “But they need to be able to take the criminals off the streets faster, for a longer time, and give them tougher punishments.”

Some fear, however, that the panic over violent gang crime risks creating a mindset among police where they shoot first and ask questions later. Following the death of Eric Torell, there were warnings the police were ramping up their tactics to “meet hard with hard”.

“Officers had told me they were worried a tragedy like this would happen because of the police focus on extreme situations,” says Stefan Holgersson, who describes himself as a whistleblower inside the police force.

Holgersson says the police risk creating nervous officers who expect the worst and therefore are more likely to put themselves and others in danger.

“When you train for gang or terrorist activity, you get that picture in your mind that this is how to act in stressful situations,” Holgersson says. “And when the police act hard, they risk turning people into enemies of the police. Their training is making things worse.”

Holgersson’s point of view appears to be supported by statements such one from an officer commenting on Eric Torell’s death. “If we encounter something we believe is a firearm, then we will shoot to eliminate the threat,” the officer told Swedish media. “You do not do this by hitting someone in the leg. We aim for the chest; that’s how we’ve practised.”

Away from the political debate, Swedish police officers are patiently working to restore relationships with communities where people fear to come forward as witnesses to violence. The number of shootings fell last year compared with 2017, points out Ch Supt Gunnar Appelgren, who has led the police operation in areas of Stockholm worst affected by violent gangs.

“We have more police on the streets, building relationships, earning trust, working with local councils and businesses,” says Appelgren. “But it goes unnoticed because you have the shootings, which are extremely high profile.”

The three police officers on trial for the death of Eric Torell stand accused of not following procedures and failing to stop shooting when he turned his back.

Eric’s mother, Katarina Söderberg, says she cannot understand how they failed to see her son had Down’s syndrome.

He was like a three-year-old, she says, and the only word he knew was “mum”. “Eric had no understanding of danger. His starting point was always that everyone was kind.”