The Netherlands needs to be more aware of the potential dangers presented by lone wolves with mental health problems such as student Tarik Zahzah, who forced his way into the Nos television studios with a fake gun, a leading psychologist says.

Hjalmar van Marle, who is a professor at Erasmus University in Rotterdam, referred to last week’s incident involving a ‘confused’ man in Groningen who threatened passerbys with a knife. He died after cutting himself and jumping into a canal.

In addition, the man now being questioned in connection with the murder of former health minister Els Borst is known to have severe psychiatric problems, Van Marle pointed out on Nos news.

‘We need to be extra alert. Just as we are when it comes to suspect packages at railway stations,’ he told Nos. Healthcare professionals must also give extra attention to people with these sorts of issues, he said.