A heavily armed assailant ranting about Jews tried to force his way into a synagogue in Halle, Germany on Wednesday, before he killed two people nearby. AP Photo/Martin Meissner.

HALLE, GERMANY – German investigators were puzzled on Thursday, over how the suspect in a botched attack on a synagogue on Judaism’s holiest day managed to amass at least 4 kilograms of explosives and acquire four firearms, an arsenal they said he planned to use in a massacre.

While many questions remain about the suspect, German officials sought to reassure a shaken Jewish community after Wednesday’s attack in the eastern city of Halle. They invoked Germany’s historical responsibility from the Holocaust as they vowed better security and urged the nation to stand behind its Jews.

The attacker, a German identified by prosecutors as Stephan B., tried but failed to force his way into the synagogue as up to 80 people were inside. He then shot and killed a 40-year-old German woman in the street outside and a 20-year-old man at a nearby kebab shop.

He fled the city, wounding another two people in a small town near Halle where he abandoned his car and driving onward in a stolen taxi. He was arrested about 1½ hours after the attack as he got out of the taxi, which had been in an accident.

“What we experienced yesterday was terror,” said Peter Frank, Germany’s chief federal prosecutor. “The suspect, Stephan B., aimed to carry out a massacre in the synagogue in Halle.”