German Christian Democratic Union (CDU) politician Walter Lübcke, who recommended anti-mass migration Germans to leave the country, was found dead at his house, having been shot in the head.

The 65-year-old, who became well-known for his support of CDU Chancellor Angela Merkel’s open borders policy during the height of the migrant crisis, was found dead on Sunday on the terrace of his home in a village near Kassel, French newspaper Le Monde reports.

During the migrant crisis, Lübcke caused controversy after attacking those against mass migration saying: “Those who do not share these values ​​can leave this country at any time.”

So far, investigators say they have no suspects in the case and are still investigating the incident. A colleague of Lübcke claimed that the politician had received many threats from the Reichsbürger group, a grouping of sovereign citizens who do not recognise the legitimacy of the post-war German constitution.

Last year, the German domestic intelligence agency claimed that there were as many as 16,500 people involved in the Reichsbürger movement across the country.

German Populist Party Chairman Hospitalised in ‘Assassination’ Attempt https://t.co/zMJhJ7jEcM — Breitbart London (@BreitbartLondon) January 8, 2019

German Federal President Frank-Walter Steinmeier reacted to the murder saying: “We do not know anything about the origin of the crime, but there is something cynical, detestable, disgusting, and obnoxious about the satisfaction some people have expressed on social networks when they learn of his death.”

Several social media users had expressed celebrations over the death of the CDU politician, angering Steinmeier who added: “To be honest, I would like more indignation than I see at the moment, as well as more sense of responsibility on the part of platforms that continue to spread such feelings of hatred.”

The case is just the latest incident of violence toward politicians in Germany. Earlier this year, populist Alternative for Germany (AfD) MP Frank Magnitz was attacked by masked men in what some referred to as an assassination attempt.

Lübcke is also not the first open borders politician to be violently attacked. In October 2015, Cologne mayor Henriette Reker was stabbed in the neck by an attacker opposed to her mass migration policies.