German authorities say they have arrested a dual German-Russian citizen on suspicion of carrying out last week's bomb attack against a bus carrying players from a top soccer team.
Federal prosecutors say the suspect, identified as 28-year-old Sergej W., was detained on April 21 near the southwestern town of Tuebbingen and charged with attempted murder, causing an explosion, and serious bodily harm.
He was hoping to make money if the price of the soccer club's shares fell on the stock market, a statement said.
Three bombs went off near a Borussia Dortmund team bus outside the city of Dortmund on April 11 as it was heading to a stadium for a Champions League match against Monaco, injuring a player and a police officer.
The prosecutor's office said the suspect had bought 15,000 put options for shares in the club. The contracts would have entitled him to sell the shares by June at a predetermined price, potentially resulting in a substantial profit if their value fell in the meantime.
"A significant share price drop could have been expected if a player had been seriously injured or even killed as a result of the attack," the statement said.
According to investigators, the suspect made his market bet on the day of the attack using an IP address traced to the hotel where the team had been staying. He had taken out a loan to fund his purchase of the put options.
The statement said the man also booked a room at the hotel and placed three explosive devices, packed with metal pieces, along the route the bus would take to reach the stadium for their first-leg match against Monaco.
Prosecution spokeswoman Frauke Koehler later told reporters that there was "no indication so far" of accomplices but said investigators did not rule out that others were involved.
The incident initially was treated as a terrorist incident after a note hinting at an Islamist connection was found at the scene.
But an Iraqi man who was detained and suspected of being a member of the extremist group Islamic State (IS) was found to have no connection with the attack.
Borussia Dortmund defender Marc Bartra, a Spaniard, underwent wrist surgery after the bomb attack. A police officer accompanying the bus was also injured.
The price of shares in the soccer club did drop after the attack, falling from 5.738 euros to a low of 5.421 euros. The share price then recovered slightly but dropped again after Borussia Dortmund was eliminated from the Champions League.