BERLIN (AP) — German lawmakers plan to investigate possible mistakes made by security agencies in their handling of two neo-Nazis suspected of killing a regional politician last year.

Opposition lawmakers in the central state of Hesse announced Thursday that they want to hold a parliamentary investigation into what police and domestic intelligence officials knew about the two suspects, whose trial began this week.

Stephan Ernst, a 46-year-old German man, is accused of the murder, attempted murder, serious bodily harm and firearms offenses. A second man, identified only as Markus H. because of privacy rules, is accused of accessory to murder and breaking firearms laws.

Prosecutors say the men were behind the slaying last June of Walter Luebcke, a member of German Chancellor Angela Merkel’s center-right Union bloc who had spoken out in favor of helping refugees. Ernst is also accused of stabbing an Iraqi asylum-seeker in January 2016.

Hesse lawmakers want to know why Ernst, who had previous convictions for violent anti-migrant crimes, had dropped off the radar of security agencies, and why they didn’t intervene when Markus H., whose far-right views were also known, acquired firearms.

Frankfurt’s regional court on Thursday reviewed a police video recording of Ernst confessing to Luebcke’s killing following his arrest. He later retracted the confession.