Saturday night turned into a horror movie at London’s Leytonstone underground station as an attacker slashed a person’s throat while shouting “this is for Syria.” Police, who had difficulty detaining the man with only a Taser, are now treating the incident as a terror act.

The attack took place in the ticket hall at Leytonstone station. Witnessed described a horrific scene, with a pool of blood on the floor and the attacker shouting, while threatening to stab others.

The victim, who reportedly had his throat cut, was transported to a hospital and remains in a serious condition with multiple stab wounds, according to paramedics.

“We are treating this as a terrorist incident,” the head of the London police’s Counter Terrorism Command, Richard Walton, said in a statement.

A total of three people were injured in the incident – one seriously and two with only minor wounds, according to police.

London police declined to comment on the reports that the attacker was shouting comments about Syria.

Police used a Taser on the suspect to apprehend him, as he repeatedly resisted arrest. A video emerged showing the attacker scuffling with an officer.

WARNING: GRAPHIC FOOTAGE

#London ‘This is for #Syria’: Machete-wielding man attacks London tube, police probing ‘terrorist incident’ pic.twitter.com/niZFIT57n1

— Wally Sarkeesian (@gagrulenet) December 5, 2015