LONDON (AP) — The teenager accused in a stabbing attack that killed three girls at a Taylor Swift-themed dance class in England has been charged with producing the deadly poison ricin and now faces a terrorist offense for possessing a jihad training manual, police said. Tuesday.

Axel Rudakubana, 18, who is accused of killing three girls and stabbing 10 other people on July 29, produced the deadly poison ricin which was later found in his home, Merseyside Police said. Police also discovered he had a computer file with an al-Qaida training manual titled: “Military Studies in Jihad Against Tyrants.”

Ricin is derived from the castor plant and is one of the deadliest toxins in the world. It has no known vaccine or antidote and kills cells by preventing them from making proteins.

Police stressed that the stabbing attack was not classified as a “terrorist incident”, which would require a motive to be known.

The stabbing happened in the first week of the summer holidays when the girls, aged between six and 11, attended a two-hour session led by a yoga instructor and a dance instructor.

Witnesses described hearing blood-curdling screams and seeing bloodied children running from the studio.

The first officers who arrived were shocked to find so many victims, said Police Chief Serena Kennedy.

Rudakubana already faced three murder charges over the July deaths of Alice Dasilva Aguiar, 9, Elsie Dot Stancombe, 7, and Bebe King, 6, in the seaside town of Southport in north-west England.

He was also charged with 10 counts of attempted murder for the eight children and two adults who were injured.

The stabbings were used by far-right activists to stoke anger at immigrants and Muslims after misinformation spread on social media identifying him as an asylum seeker and misreporting his name.

The violence spread from Southport and led to riots in England and Northern Ireland that lasted a week.

Rudakubana was born in Wales to Rwandan parents, police said. British media reported that he was raised Christian.

Dr Renu Bindra of the UK’s Health Safety Agency said there was “no evidence that victims, responders or members of the public were exposed to ricin, either as part of the incident or afterwards”, and the risk to the public of was low. No ricin was found at the scene of the stabbing.

Ricin is estimated to be 6,000 times more poisonous than cyanide and can be fatal when inhaled, ingested, injected or swallowed. Two million ounces – about the weight of a grain of salt – is enough to kill an adult.

Several people have been tried around the world in recent years, accused of trying to use ricin for murder or terrorist plots, but examples of its successful use are rare.

Bulgarian defector Georgi Markov was killed in London in 1978 when a pin-sized pellet laced with ricin was injected into his thigh – said to be by a rigged umbrella.

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This story has been corrected to reflect that the terror charge is linked to the jihadist training manual.