BERLIN (AP) — A 28-year-old German-Russian citizen was arrested Friday in Germany on suspicion of bombing the bus carrying the Borussia Dortmund soccer team in an attack last week that officials alleged was motivated by financial greed, prosecutors said.

A Dortmund player and a policeman were injured in the triple blasts last week as the bus was heading to the team's stadium for a Champions League game. Investigators found notes at the scene claiming responsibility on behalf of Islamic extremists, but quickly doubted their authenticity.

Federal prosecutors said the suspect, identified only as Sergej W. in keeping with German privacy law, was arrested by a police tactical response team early Friday in or near the southwestern city of Tuebingen.

He faces charges of attempted murder, causing an explosion and serious bodily harm.

Prosecutors said they planned to make a statement later Friday, but revealed that the suspect had taken out a loan and bought a large number of so-called put options for shares of Borussia Dortmund, betting on a drop in the share price.

"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," they said.

Ralf Jaeger, the top security official in North Rhine-Westphalia state, said the suspect had hoped to earn millions.

"The man appears to have wanted to commit murder out of greed," said Jaeger.

Prosecutors said they traced the computer used to purchase the put options to the luxury hotel in Dortmund where the team had been staying. They said W. had also booked a room there and placed three explosives, packed with shrapnel, along the route the bus would take to reach the stadium for their first-leg match April 11 against Monaco.

"The explosive devices were detonated at the optimum time," prosecutors said, noting that the team bus was equipped only with security glass and not reinforced glass. Several windows on the bus were shattered, injuring defender Marc Bartra. A police officer accompanying the bus also suffered trauma.

The club thanked authorities in a statement. "The fact that no further people were injured or killed was, as we now know, purely a matter of luck," it said on Facebook.

Captain Marcel Schmelzer said the team hoped to learn further details about the background to the attack. "This information is important to everyone who sat in the bus because it would make it significantly easier to process (what happened)," he was quoted as saying.

After the three identical notes claiming responsibility for the attack were found at the scene investigators initially considered the possibility that it might have been the work of Islamic extremists.

The notes demanded that Germany withdraw reconnaissance jets assisting the fight against Islamic State group and close the U.S. Ramstein Air Base in Germany. But experts said the letter's mix of correct, complicated German and obvious mistakes suggested it was a red herring — as were two subsequent claims pointing to left-wing and right-wing extremists.

Still, a 26-year-old Iraqi man detained after the attack was ordered held on suspicion of membership of IS. The man, identified only as Abdul Beset A., allegedly led a unit of about 10 IS fighters involved in preparing kidnappings, extortions and killings in Iraq, before traveling to Germany in early 2016.