German news magazine Der Spiegel on Wednesday fired reporter-editor Claas Relotius for inventing stories and distorting facts. The magazine said it has published almost 60 articles by Relotius, who wrote his first article for the publication as a freelancer in 2011.

The publication said the matter came to light when Relotius’ colleague Juan Moreno grew suspicious of the authenticity of an article on an American vigilante group that they were working on.

“Relotius falsified his articles on a grand scale and even invented characters, deceiving both readers and his colleagues,” the magazine said. “This has been uncovered as a result of tips, internal research and, ultimately, a comprehensive confession by the editor himself.”

Moreno reportedly informed the magazine’s administration and conducted an investigation of his own into the article the two were reporting on.

The magazine said Relotius “committed his deception intentionally, methodically and with criminal intent”. The magazine will add a notification about the development in all the articles published by Relotius online until the investigation into the matter is completed. It also called on readers to contact them with any information on the matter.

According to the magazine, Relotius told them that he regretted his actions and was deeply ashamed, The Guardian reported. “I am sick and I need to get help,” Der Spiegel quoted him as saying.