BERLIN (AP) — A far-right extremist who killed two people in the German city of Halle three years ago after attempting to attack a synagogue has been moved to a new prison hundreds of kilometers (miles) away following an apparent jailbreak attempt.

Stephan Balliet, 30, was taken to the Augsburg-Gablingen prison in Bavaria under heavy guard early Tuesday.

Balliet took two guards hostage Dec. 13 at the Burg high-security prison near the eastern city of Magdeburg. Other guards overwhelmed him within an hour, authorities said. He was injured in the incident, while the hostages were freed unharmed.

State security officials in Saxony-Anhalt, where the Burg facility is located, said that based on what Balliet could be heard saying on surveillance footage, they assumed he was trying to escape from the prison.

Armed with multiple firearms and explosives, Balliet had attacked the synagogue in Halle on Yom Kippur, Judaism’s holiest day, in 2019. After failing to break down the synagogue door, he killed a passer-by and a man inside a nearby fast-food restaurant.

The antisemitic attack that Balliet broadcast live on the internet caused shock in Germany, which has sought to make amends for the Holocaust and to protect Jews who returned to the country after World War II.

Balliet tried to escape from another prison while still on trial. He was sentenced to life in prison in 2020.

Germany’s top security official called on the country’s prison operators to review their security measures after last week's hostage-taking.