The European law enforcement agency says the bomb-maker used “the same modus operandi” in attacks on stores in France, Belgium and The Netherlands in May, in Germany in June, and Czech Republic on Sept. 2.

Europol described the suspect as an Eastern European man, 175 centimeters (5 foot 9 inches) tall, with fair, short-cropped hair, 35-45 years old, and wearing glasses. In each attack he left a homemade bomb and quickly left the store.

It said Saturday some bombs were potentially lethal, though not all detonated. Two people were injured in the German attack.