Computer engineer Lewis Daynes (19) admitted to the murder of Breck Bednar (14) after changing his plea on the day he was due to stand trial in Essex, England.
Breck was stabbed to death at a flat in Grays, Essex, in February. It is understood he met Daynes after they played online video games together.
Barrister Richard Whittam QC told the court it was the prosecution’s case that the murder “involved a sexual and sadistic motivation”.
Family members said Breck, from Caterham in Surrey, left home after arranging to meet a friend online.
He was found more than 30 miles (48km) away in Grays with a fatal stab wound to the neck on February 17th.
Daynes replied “guilty” after the Chelmsford Crown Court clerk read the charge to him.
Mrs Justice Cox said Daynes would be sentenced on January 12th.
Speaking outside court, the victim’s mother, Lorin LaFave, said: “I want Breck’s tragedy to open the eyes of everyone to recognise the dangers of online predators. It is a very real danger today.”
Ms LaFave and the victim’s father, oil futures trader Barry Bednar, originally from Houston, Texas, were both in court to hear Daynes’s guilty plea.
Breck, who was a student at St Bede’s School in Redhill, Surrey, was “extremely gifted in computing, electronics, and engineering”, his family added.
PA