The man who was arrested following Friday’s shooting at a day centre for adults and children with psychiatric problems had emailed a television show shortly before he shot dead two people.

The man, 38-year-old John S, did not say what he was about to do, but did admit to killing a shoemaker in Vlissingen earlier in the week, RTL Boulevaard said. He also sent photographs of his first victim and gave details only the killer would have known.

S said he had met his Vlissingen victim in a chat room for gay men and that he had killed him to test out his weapon. He also said he had told his doctor and local mental health service officials about his obsession with guns and that he had only dared get hold of one a couple of weeks ago.

In addition, he told the programme, it had been ‘war in his head’ for years and that he had tried to kill himself five times. One of those attempts was ‘related to the care farm’, he said. Police confirmed on Friday he had been a patient there.

A 34-year-old woman and a 16-year-old girl were killed, and a 20-year-old woman and 12-year-old boy were seriously injured in the attack, which took place shortly before 11 am on Friday.

The two people who survived the shooting are seriously ill in hospital.

‘Alblasserdam is in shock,’ mayor Jaap Paans told a press conference on Friday. ‘Many people witnessed this terrible event. I have spoken to relatives, clients, volunteers and workers and they have spoken about the fear and the sorrow they experienced.’

The zorgboederij, or care farm, is a concept which allows people with problems or disabilities to work with animals or on the land, as occupational therapy.