(JTA) — A demonstrator in Frankfort, Germany, used a police megaphone to shout anti-Israel slogans after duping police.

Police said the demonstrator had agreed to calm down a violent protest Saturday but instead shouted “Child murderer Israel” and “Allahu akbar!” — Arabic for “God is great” — a Frankfurt police spokeswoman told The Associated Press.

“We as police had come up spontaneously with this unusual method and he abused it — we didn’t expect that,” the spokeswoman, Virginie Wegner, told AP.

The crowd of more than 2,000 protesters, who were waving Palestinian flags and calling for a boycott of Israeli products, followed the police car while cheering and repeating the slogans, according to AP.

Dieter Graumann, head of the Central Council of Jews in Germany, condemned the incident.

“I’m shocked that a German police car was used to spread hatred and agitation,” Graumann said, according to AP. “It was a big mistake that the police let themselves be abused for this.”