The Portuguese suspect, named as José Luis Dantas de Carvalho, had repeatedly beaten his 30-year-old wife, known as Maria D., online news site 20 Minuten reported.
She was shot dead in the car park of Schübelbach-Buttikon train station on Wednesday. Her killer is still at large.
After several years of abuse, in October 2011 Maria finally managed to escape with her 13-year-old daughter to live in a separate flat in a neighbouring village.
But rather than leave them alone, as she had hoped, her husband began to follow her everywhere.
"At work, in front of my house, at her home – he turned up everywhere, watched, harassed and threatened her," a close friend of Maria’s told the website.
De Carvalho was arrested three times following complaints by Maria to the police. He was given a restraining order but paid it no attention. It was then that he began to send her death threats via text messages and Facebook.
Eventually he was taken into custody and given a psychiatric evaluation. However, this report found him to pose only a "moderate" risk and he was released. But just three weeks later, the fugitive became the prime suspect in the murder of his wife.
Questions are now being raised about the decision-making process that led to his release.
“It should not have happened,” senior prosecutor Benno Annen told the website.
He explained that the authorities were of the opinion that the suspected killer did not have a weapon. It may be that the weapon was obtained the weekend before the shooting, when de Carvalho was in Portugal.
“Why else would you drive 400 kilometres in three days?” Maria’s friend asked.
Maria’s new boyfriend, a man she had met at her work, and her daughter have been taken to a safe house as it is feared that they both may still feature on de Carvalho’s hit list.