German media reported that the suspect stayed at a hotel next to the explosion site and behaved suspiciously while other guests panicked after hearing the triple blast.
Sergey V. supposedly wanted to increase his profits by speculating on falling Borussia shares after the attack, receiving 3.9 million euros ($4.1 million), according to prosecutors. The suspect had acquired 15,000 shares just before the incident using borrowed money. He may have detonated the bombs from his hotel room, which was booked in advance to ensure the room's windows faced the street where the explosions went off. The police are now searching for two potential accomplices, also of Russian origin.
Earlier leads followed by investigators were related to Islamist radicals and the German involvement in the US-led coalition in Syria. The far-left Antifa movement has also allegedly claimed responsibility.
On April 11, three explosions hit a bus carrying Borussia Dortmund players but only injured two people. The team was expected to play against Monaco FC in a quarterfinal of the Champions League. The game was rescheduled due to the incident.