In a strange twist, German police say the man suspected of bombing a bus carrying the Borussia Dortmund football team was a speculator who had hoped to profit by sending shares in the team plummeting.

Members of an elite police unit arrested the suspect, a 28-year-old dual German-Russian national identified as Sergej W., on his way to work near the southwestern German city of Tuebingen Friday, and charged him with charged with attempted murder, inflicting serious bodily harm and causing an explosion.

On April 11, the day of the attack, the suspect had bought 15,000 put options on the team’s shares, according to the federal chief prosecutor’s office. The options, which give the investor the right to sell shares for a specified price on or before a specified date, would have significantly increased in value if the club’s share price dropped sharply.

The team bus was heading to the club’s stadium for a Champions League match against AS Monaco when three bombs packed with metal pins exploded near their hotel, wounding Spanish defender Marc Bartra, who required wrist surgery.

An Islamist motive was initially suspected after letters were found nearby which mentioned the caliphate and the ISIS terror attack on a Christmas market in Berlin. But earlier this week police said these appeared to have been planted in an attempt to mislead investigators.

Prosecutors said the suspect stayed in the hotel where the team were based, the l’Arrivee hotel, at the time of the attack, and had bought the options on a computer using the hotel’s IP address.

Germany’s Bild newspaper reported that when checking in to the hotel, the suspect had turned down the first room he was offered in favor of one with a clear view of the road where the bombs were installed. The newspaper reported that he aroused suspicions in the aftermath of the attack when he ordered a steak in the restaurant, while other guests were panicking.

An online bank also flagged the suspect’s purchase of the options to police as potentially suspicious.