The teenager who Austrian authorities say planned to unleash a "bloodbath" at a Taylor Swift concert in Vienna this week only recently showed hints of being radicalized on the Internet into committing acts of violence, according to people who knew him.

Identified by Austrian media as Beran A., the 19-year-old was said by neighbors to have been reserved but friendly before his arrest this week thrust him into international headlines when authorities announced they had thwarted the planned attack.

His neighbors in Ternitz, a small town some 80 kilometers southwest of Vienna, were stunned by the accusations leveled against him, although several said that he had grown a long beard and become more serious in the run-up to the foiled plot.

"Only recently did he become a bit unusual," said Nicole Morgenbesser, a 33-year-old mother living nearby.

Morgenbesser said the youth, who is from a family of North Macedonian origin, had always cheerfully said hello to her on the street or waved from his car - until a few weeks ago.

"He stopped greeting me," she said, expressing sorrow for the parents of the young man, who lived with him in a bright, freshly painted terraced house at the end of the street.

Austrian officials handling the investigation said the online self-radicalization of the youth had occurred quickly, leading to him swearing a pledge to ISIS in a video and telling people he had "big plans" after quitting his job last month.

Described as the prime mover behind the plan to attack a soccer stadium where Swift was on Thursday due to kick off a three-day stint in Vienna, he was the oldest of four teenagers so far detained by police, the others being 18, 17 and 15.

"You always hear about these sort of things, but it's something else when this happens on your own front door," said Christian Samwald, the mayor of Ternitz, a town of around 15,000 people nestled among lush fields of sunflowers in a river valley enclosed by the green mountainsides of the Gutenstein Alps.

Austrian investigators said the 19-year-old had made a full confession. It is unclear if he has a lawyer and state prosecutors said they had no information on the matter.

Samwald said there had been shock and dismay in Ternitz about the news because there had been no prior indication that the youth harbored any radical inclinations.

"The lesson is it's difficult to prevent someone from being radicalized on the Internet," he said.

A neighbor of the main suspect speaks to a Reuters journalist, following the cancellation of three Taylor Swift concerts at Happel stadium in Vienna after the government confirmed a planned attack at the venue, in Ternitz, Austria, on Aug. 8, 2024. (Reuters/Elisabeth Mandl)

The youth apparently began an apprenticeship after the family moved from Vienna to Ternitz a few years ago, without attending school there, the mayor said.

The company identified by residents as his employer did not answer calls or respond to a written request for comment.

Dozens of residents were temporarily ejected from their homes on Wednesday morning so that armed, masked police could raid the suspect's house, seizing chemicals, machetes and devices the plotters planned to use in the attack.

About an hour earlier, police had arrested the youth, with what one neighbor described as a "shout" and "bang" outside just a few meters away from her front door.

Reuters spoke to over a dozen neighbors who said the youth's parents had been away at the time. Police, they said, had told them there was a gas leak so the locals, which included residents of a retirement home, would leave their houses.

Residents said the parents had returned after the raid and they were believed to be inside the little two story house as a raft of accusations was read out against their son in Vienna.

Knocks on the door went unanswered, and there was no sign of movement behind the lace curtains and partly shuttered blinds.

Close relatives of the family with roots in the North Macedonian town of Gostivar, hundreds of miles to the southeast of Ternitz, were also looking for answers.

"It looks someone has manipulated him because we are not such a family," said one of them in the village of Cajle on the outskirts of Gostivar. "We still cannot believe what has happened."