The 14-year-old girl was from Fort Wayne, authorities said. By Meredith Deliso A German teenager has been arrested on suspicion of murder in connection with the death of a 14-year-old girl in the United States, according to the FBI.

The 18-year-old is suspected of manipulating an Indiana teen over a social platform into harming herself and taking her own life, according to prosecutors in Germany.

The FBI said Friday it worked with local Indiana authorities to investigate the teenager's death and shared evidence with German authorities. The suspect was arrested on Thursday, prosecutors in Hamburg said. The girl was from Fort Wayne, according to the Fort Wayne Police Department, which investigated her death.

"After a thorough criminal investigation, the Homicide Unit identified a suspect who contributed to the juvenile’s death," the police department said in a statement Friday. "Investigators identified him as an adult male residing in Germany and collaborated with federal partners at the Federal Bureau of Investigation and authorities in Germany." Officials have not publicly identified the girl or the suspect.

Hamburg prosecutors said the German national, who was 17 at the time of the alleged offenses, is suspected of manipulating "a psychologically vulnerable" American girl through the social platform Discord between September and October. ABC News has reached out to Discord for comment.

Prosecutors are investigating reports alleging the suspect demanded the girl to inflict severe self-harm and then to take her life on Oct. 2. Whether the death was recorded "remains a subject of the ongoing investigation," Hamburg prosecutors said.

The suspect allegedly tried to obtain footage of the death and "threatened the girl's social circle, stating that he would otherwise publish her personal data as well as compromising images of her," prosecutors said.

Prosecutors believe the man sought to use the footage to gain status within or to gain entry to the so-called "NMK" (Nefarious Maniac Kult), which they said is modeled on groups linked to the online "COM network" such as "764." Last week, authorities in Fort Wayne warned the community about what they called the online extremist network 764 and "splinter groups" that they said target vulnerable teens through social media and gaming websites.

"The most concerning thing that we're seeing is these groups are encouraging these young people that they're targeting to commit self-harm, cutting, carving symbols and words into their bodies," Fort Wayne Police Department Det. Brian Martin said at a news conference on Oct. 14.

"They're encouraging our children to send explicit photos, nude photos of themselves. They're encouraging our young people to commit self-mutilation. They are encouraging to harm family pets, to torture pets," he continued.

He added, "They're such predators that they want this to be video recorded or live streamed to them while they're doing this." Previously, Discord has said that disrupting the 764 network and affiliate groups "has been among Discord's highest priorities" and that it has taken steps to remove thousands of "servers" and invested in new ways to detect the groups.

If you are struggling with thoughts of suicide or worried about a friend or loved one, call or text the Suicide & Crisis Lifeline at 988 for free, confidential emotional support 24 hours a day, seven days a week.