Saturday's attack took place as the train neared the Swiss town of Salez, close to the border with tiny Liechtenstein.
Six people and the attacker were wounded. The 27-year-old assailant and a 34-year-old woman he had attacked later died of their injuries.
Swiss daily Blick reported last night, without citing sources, that the attacker had lived for around three years in Liechtenstein, which has close ties to Switzerland.
Police in St Gallen canton (state) said today that he officially was registered as living in a neighbouring Swiss canton.
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