Reynhard Sinaga, a 36-year-old PhD student from Indonesia, was found guilty of 159 sexual offences against 48 men.
He picked up his victims outside clubs in Manchester and lured them to his flat, where he drugged and assaulted them while filming the attacks.
On Monday, a judge jailed Sinaga for life, with a minimum term of 30 years.
As Sinaga's family and friends come to terms with his fate, they have painted a picture of his life in Indonesia before he became a serial sexual predator.
Supiyatna, the principal of Depok 1 Public High School confirmed that Reynhard Sinaga was a graduate student from 1998 to 2001, spoke to an Indonesian journalist on Thursday (January 9).
According to him, there are no distorted characteristics or behavior that Reynhard displayed during his education at this school.
Reynhard is known as an ordinary teenager like his classmates.
Although somewhat smart and a bit stubborn, Reynhard was not an outstanding student.
"Reynhard studied at SMAN 1 Depok for 3 years from 1998 and graduated in 2001.
His association was ordinary, not too prominent.
He was stubborn but not too stubborn, smart but not too smart, so he didn't have to get special attention from his teachers.
He is a person who is flexible, easy to get along with so many friends.
When related to the case he is doing at this time we feel quite concerned and shocked as not describing the Reynhard we know," Supiyatna said.
After graduating in 2001, Reynhard continued his education by studying at the University of Indonesia, majoring in Architecture.