BERLIN -- A 28-year-old German-Russian citizen took out a five-figure loan to bet that Borussia Dortmund shares would drop, then bombed the team's bus in an attack he tried to disguise as Islamic terrorism in a scheme to net millions, German officials said Friday.

Dortmund's Marc Bartra and a policeman were injured in the triple blasts on April 11 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.

German federal prosecutors said in a statement that the suspect, identified only as Sergej W. in keeping with German privacy law, was arrested by a police tactical response team early on Friday in the state of Baden-Wurttemberg, near the southwestern city of Tuebingen.

Prosecutors said they have found no evidence that others were involved in the plot and they believe the suspect acted alone.

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

"We are working on the assumption that the suspect is responsible for the attack against the team bus of Borussia Dortmund," prosecutors' spokeswoman Frauke Koehler told a news conference on Friday.

She said the man came to the attention of investigators because he had made "suspicious options purchases" for shares in Borussia Dortmund, the only top-league German club listed on the stock exchange, on the same day as the April 11 attack.

W. had taken out a loan of "several tens of thousands of euros" days before the attack and bought a large number of so-called put options, betting on a drop in Dortmund's share price, she said.

"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," according to prosecutors, though Koehler said the precise profit W. might have expected was still being calculated.

Prosecutors said 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 after the attack.

"We'd like to think that the suspect is responsible for the attack on the team bus. We were put on to the suspect's tracks by suspicious option deals. He in total bought three different derivatives and gambled on falling stock prices.

"He bought the majority of the derivatives on April 11, the day of the attacks. The suspect took out a loan over several €10,000. His profit would have increased all the lower the stocks would have dropped. We can't say right now how high the profit could have been exactly."

Ralf Jager, the North Rhine-Westphalia state's minister of the interior, said the suspect had hoped to earn millions.

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

Prosecutors added that the suspect had booked a room in Dortmund's team luxury hotel from April 9-13 and then April 16-20, the time-frame during which a second leg would have been played at Dortmund had their Champions League quarterfinal draw necessitated it. They said W. 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.

"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,'' prosecutors said in their statement.

Prosecutors said that the three blasts had detonated at the time the bomber had intended, but that the second blast occurred around one metre above the ground, limiting the damage.

The bombs were filled with metal pins around 70 millimetres long, with one pin found 250 metres away from the blast.

"We can't conclusively say which kind of explosives he used," Koehler said. "The investigations are still ongoing. They are complex since all of the explosives were used up in the explosion. Knowledge about it can only be gained by indirection like soil samples.

"At this stage, there are no leads to possible abetters or accomplices. But we will keep an eye on it."

Borussia Dortmund's bus was stopped after a series of explosions that shattered windows last week. Getty

Investigators from the Federal Prosecutor's office in Germany, the Federal Criminal Police and North-Rhine Westphalian state police had been following the lead after receiving information from the finance sector as well as from a bank suspecting money laundering, according to Spiegel, which broke the story early on Friday.

The day after the attack, German public TV station ARD reported that there had been an abnormality on the stock market just prior to the explosions with somebody buying options at the Frankfurt stock exchange.

ARD said that the buyers must "either have been extremely inexperienced or expecting a sharp fall in prices."

The three explosions near the Dortmund team bus injured two people, including Bartra, and investigators later said that the attack could have caused major harm.

It was confirmed on Friday that one metal pin was found in the headrest of one of the seats in the last row in Dortmund's team bus. According to earlier reports, Bartra sat in the last row along with goalkeeper Roman Burki.

"We in particular owe it to the Borussia Dortmund team to comprehensively solve the deed and its backgrounds," Heiko Maas, the German Minister of Justice, said. "Every motive for this deed is vile. Should the suspect have tried to kill several people out of pure greed for money this would just be atrocious."

Following the attack, three identical letters were found near the scene of the attack and suggested a possible Islamist extremist motive, but investigators had doubts about their veracity.

Prosecutors added that another letter claiming the attack for a far-right background received by Berlin-based daily Tagesspiegel on April 13 also raised doubts, and could not be linked to the person behind the attack.

Dortmund CEO Hans-Joachim Watzke and club president Reinhard Rauball both expressed their gratitude to investigators.

"We hope that by arresting the suspect, the person responsible for the villainous attack on our players and staff members has been caught," the pair said in a joint statement on the club's official website.

Club captain Marcel Schmelzer added that the team hoped "to learn about the actual reasons behind the attack," adding: "For everyone on the bus this information would facilitate the process of coping with it."

Speaking on the club's in-house TV channel, sporting director Michael Zorc said: "My first thought is relief. I hope it helps processing the events."

Speaking at a prematch news conference to preview Dortmund's trip to Borussia Monchengladbach in the Bundesliga, Thomas Tuchel said that solving the case will help the team to process the events and move on.

"I cannot comprehend the [alleged] motive emotionally or rationally. I don't know whether it is a fact as of now, so it's still important to use the subjunctive," Tuchel said. "I'm convinced that it is very important for everyone who was directly involved [in the attack] that the case is solved and it seems as though it's close to being solved," Tuchel added. "I know from many players that this would help them [to process the events]. So it's a good feeling that there apparently was a breakthrough in the investigation."

Asked about the return to normalcy if the new lead in the investigation holds true, Tuchel added: "I can only speak for myself as there is no panacea for it. I still believe that it's very important to us to know the backgrounds [of the attack], the motive and the perpetrator to process the events.

"I can say that I'm personally dealing [with everything] rather well at the moment, I'm okay to also say that publicly, but I wouldn't dare to speak for my players or say the same about my players.

"It's a great achievement and very courageous of the team and players that they could focus on tactics, on training and other sporting matters concerning the match ahead of Monaco.

"However, we cannot expect the same [diligence] of the players as we usually would demand it. Not everyone is feeling the same as I am and everyone has a right to take the time he needs, which is why the upcoming match in Gladbach has to be put in parentheses. It will require a lot of sensitivity from us to determine in how far we can confront players with criticism. We can still sense that a lot of players are still under the impression [of the attack].

"And if we talk about the two legs against Monaco that this was the deciding advantage for Monaco, who deservedly progressed [to the semifinals]. We saw a team that was on a level with us, but whose minds were free and determined to seize the chance of their careers. Meanwhile, our team was completely taken out of their action frame of reference eight days ago. We simply couldn't muster the necessary determination and weren't worry free enough to reach the semifinals of such a difficult competition."

On Saturday, Dortmund are likely to be without Marco Reus in their pursuit of a top-three finish in the Bundesliga.

"It will be very close for Marco," Tuchel said. "We have to wait and see if he can start or even make the squad as he played 90 minutes against Monaco."

Borussia Dortmund trail third-placed Hoffenheim by one point in the league going into Matchday 30.

ESPN FC's Stefan Buczko contributed to this report.

Information from The Associated Press was used in this report.