London Bridge Attack: Boris Johnson Vows Action Against Convicted Terrorist

Prime Minister Boris Johnson vowed Saturday to review Britain's sentencing system after a convicted terrorist released early from prison stabbed two people to death and injured three in a London Bridge attack. Bystanders have been hailed as heroes for preventing even greater loss of life by tackling Usman Khan before police shot him dead.

Khan, a British national, was handed an indeterminate sentence for public protection in 2012, with at least eight years in prison.

He was part of an eight-man network inspired by Al-Qaeda who had plotted to bomb targets including the London Stock Exchange, and planned to take part in "terrorist training" in Pakistan.

But his sentence was quashed by the Court of Appeal in April 2013 and he received a new 21-year term, comprising a custodial sentence of 16 years and five years on conditional release.

Inmates are usually released half-way through the type of determinate sentence he was given, and time spent in custody before trial may have been taken into account.

The Parole Board said it had no involvement in his release and that it appeared to have happened automatically as required by law.

The latest attack came less than two weeks before Britain's general election, and politicians temporarily suspended campaigning.

"It does not make sense for us as a society to be putting people who have been convicted of terrorist offences... out on early release," Johnson, who became Tory leader in July, said as he visited the scene.

"We argue that people should serve the tariff, serve the term, of which they are sentenced," the prime minister added, noting the Conservatives' manifesto calls for a tougher sentencing regime.

Queen Elizabeth II said she and husband Prince Philip had been saddened to hear of the attack and expressed her "enduring thanks" to the "brave individuals who put their own lives at risk to selflessly help and protect others".