A former pupil known to police is suspected of carrying out a double stabbing at Kingsbury High School before fleeing the scene and being arrested at a nearby mosque.

The 13-year-old boy, described by officers as a British national born in the UK, was located in NW10 after worshippers alerted police to his presence. He was arrested on suspicion of attempted murder.

Detective Chief Superintendent Helen Flanagan, of Counter Terrorism Policing London, said the suspect was found in a “distressed state” inside the mosque.

She said: “We don’t believe he had a connection with the mosque. We think it is coincidental. Everyone in the mosque is supportive of the operation. We were clearly concerned the attack would have some terrorist motive. But we keep an open mind on the motive.”

Police said the suspect entered the school grounds before launching the attack inside a first-floor classroom. According to Chief Superintendent Flanagan, he sprayed a substance toward a pupil as he entered the room, then stabbed a 13-year-old boy.

“Having entered the school, he proceeded out to a first floor classroom,” she said. “He entered the classroom, and we believe he sprayed a substance towards a pupil as he entered the door.

“The suspect has then attacked another pupil, a 13-year-old in that classroom, stabbing him, and then the suspect has left, running down the hallway of the school. As he is leaving, he then attacked another victim, a 12-year-old, stabbing him before running off and away from the school.”

The two victims were taken to hospital. Police have since confirmed their injuries, while serious, are not believed to be life-threatening and both boys are in a stable condition.

Parents described scenes of chaos as pupils were kept in the playground for several hours while emergency services responded. Some students reported seeing blood inside the building, leaving many shaken.

One mother told reporters that her daughter was in a nearby classroom when the attack unfolded. “There was an alarm, everybody was scared and then there was chaos,” she said, adding that her child later saw blood smeared on a window, which she described as “very distressing.”

Another grandparent said his grandson had left the classroom minutes before the incident occurred, calling it a “lucky escape.”

It is understood the suspect may have accessed the school by climbing over a wall rather than entering through the main gate. Some parents have called for tighter security measures, including metal detectors and increased staffing.

The school closed to certain year groups the following day while officers from Counter Terrorism Policing London continued their investigation. Chief Superintendent Flanagan said: “This continues to be a fast-paced investigation and officers from Counter Terrorism Policing London continue to make inquiries into the circumstances.

“I can now confirm that the injuries suffered by the two victims, while serious, are thankfully not life-threatening and they remain in hospital in a stable condition. Our thoughts remain with them and their loved ones at this incredibly difficult time. Specialist officers are providing their families with support.”

She added that increased patrols would remain in place to reassure the local community, and confirmed the 13-year-old suspect remains in custody.