LONDON — Sudesh Amman, the man shot dead by police in what officials described as a terrorism incident in south London, had been jailed for promoting violent Islamist material and had encouraged his girlfriend to behead her parents.

Amman, 20, was named by British police as the attacker who stabbed two people before he was shot dead by armed officers who had been carrying out surveillance on him.

In November 2018 he pleaded guilty to possession of terrorist documents and disseminating terrorist publications, and the following month he was sentenced to more than three years in prison.

He was 17 and living at home with his mother and younger siblings when he first began committing terrorism offences, according to authorities. Police became aware of his activities in April 2018 and he was arrested by armed officers in a north London street a month later.

When officers examined his computers and phone, they found he had downloaded material about making explosives and carrying out terrorist attacks, according to police.

Messages showed that he had discussed with his family, friends and girlfriend his extreme views and desire to carry out an attack, often focused on using a knife, police said.

In December 2017 Amman posted a picture of Islamic State leader Abu Bakr al-Baghdadi, who was killed during a US raid in Syria in October, and told his brother in a message that "the Islamic State is here to stay."

He also described Yazidi women as slaves and said the Quran made it permissible to rape them, and in another message he encouraged his girlfriend to behead her parents.

Police said he had shared an online al-Qaeda magazine with his family and while in a discussion about school with a sibling he wrote he would "rather blow myself up". REUTERS