A youth, 16, died on Sunday after being stabbed in the heart in a Burjassot park in Valencia Province.
The Policia Nacional arrested a suspect on Monday in Lliria connection with the incident.
A knife used in the assault was thrown into a waste bin and the assailant lost his phone while fleeing the area.
A group of teenagers witnessed the attack at La Granja park and called emergency services.
One of the youngsters told the El Pais newspaper: “We put tissues on the wound to stop the blood pouring out until the police arrived.”
The group said that medics spent an hour trying to revive him without success.
They told El Pais that they’d never seen either of the two combatants before.
It’s believed the two youths arranged some kind of a showdown via social media.
The knife-wielding aggressor was said to have been accompanied by some friends, who hid behind a tree.
The eye-witnesses heard shouting and insults traded between the two youths and after the stabbing, a female cried out for help.
They claim the attacker’s friends got hold of the murder weapon and put it into a rubbish bin.
A 14-year-old told El Pais: “The aggressor wore a beard and a moustache and also seemed to be a minor.”
The Policia Nacional have not commented about the arrested suspect or the circumstances behind the killing.
READ MORE:-