British police said on Friday that one of the men who died in the Manchester synagogue attack was accidentally shot by police and that one of the injured was also shot by officers.

Two worshippers – Adrian Daulby, 53, and Melvin Cravitz, 66, – died in the attack on Thursday and three others were seriously injured. Police have identified the assailant as Jihad Al-Shamie, 35, a British citizen who came to the U.K. as a young child from Syria. They have also arrested three people.

Tributes and flowers have been piling up near the Heaton Park Hebrew Congregation Synagogue as people across Britain expressed their grief and outrage at what police have described as a terror attack.

Police shot and killed the attacker, who was armed with a knife. On Friday, Manchester Police Chief Constable Stephen Watson said one of the men who died had been accidentally shot, as well as one of the injured. The death and injury were the “unforeseen consequence of the urgently required action taken by my officers to bring this vicious attack to an end,” he said.

Prime Minister Keir Starmer visited the site on Friday with his wife, Victoria Starmer, who is Jewish. And at Westminster, flags in the House of Commons at half mast.

“The good and decent people of Manchester stand with you and we always will. There is no place for hate here and we will not have it,” said one noted posted on fence close to the synagogue.

Faraj Al-Shamie, the father of the attacker, expressed the family’s “deep shock and sorrow over what has happened.”

“The Al-Shamie family in the U.K. and abroad strongly condemns this heinous act, which targeted peaceful, innocent civilians,” he said in a post on Facebook.

Amid the outpouring of sorrow there was also fury that several pro-Palestinian demonstrations will take place over the weekend in Manchester and London, and that hundreds of people marched through both cities on Thursday waving Palestine flags.

The demonstrations have been held regularly for months and tens of thousands of people have come out to protest the Israel government’s handling of the war in Gaza and highlight the plight of the Palestinian people.

Explainer: What we know so far about the U.K. synagogue attack

There has been criticism that some demonstrators have used hate speech and expressed support for Hamas, which is considered a terrorist organization in Britain.

The government has moved to restrict some marches and it has banned one organization, Palestine Action, under terrorism legislation after alleging that members conducted a campaign of “intimidation and sustained criminal damage.”

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Prime Minister Keir Starmer and his wife, Victoria, talk to a member of the Jewish community as they visit the scene outside Heaton Park Hebrew Congregation synagogue in Crumpsall on Friday.PHIL NOBLE/AFP/Getty Images

Hundreds of the group’s supporters have been arrested in recent weeks during pro Palestinian marches in London. Another demonstration in support of Palestine Action is scheduled to take place on Saturday in Trafalgar Square.

During a visit to Manchester on Friday, Chief Rabbi Ephraim Mirvis questioned why the marches have been allowed to take place.

“We have witnessed an unrelenting wave of hatred against Jews being expressed on our streets, on campuses right across social media, in some of the media,” he told the BBC. “You cannot separate the words on our streets, the actions of people in this way and what inevitably results which was yesterday’s terrorist attack. The two are directly linked and therefore we call on the government yet again, we say get a grip on these demonstrations, they are dangerous.”

Deadly Manchester synagogue attack raises fears about growing antisemitism in U.K.

Home Secretary Shabana Mahmood called on organizers to cancel planned marches for the weekend, and she criticized people who demonstrated on Thursday.

“My own feeling was that was fundamentally un-British, on such a day – with an antisemitic terrorist attack in our country – I would have wanted to see people to take a step back,” she told reporters on Friday. “I would still call on people to show some love and some solidarity to the families of those who have been murdered and to our Jewish community.”

Ms. Mahmood acknowledged there was little the government could or should do to stop people from legally protesting. “I can take my lead from the police, if they were to tell me there was an inability to respond and to police the protests, then there are powers that are available,” she explained.

Ms. Mahmood also rejected suggestions that the recent decision by Britain, Canada and other countries to recognize a Palestinian state, has encourage antisemitism.

“The only person responsible for this devastating attack on our Jewish community is the attacker himself,” she said adding that the government was determined to pursue a diplomatic solution to end the war in Gaza. “Far too many lives have been lost. We want to see a secure and safe state of Israel alongside a state of Palestine,” she said.

London’s Metropolitan Police have also asked organizers to hold off on Saturday’s event.

“The horrific terrorist attack that took place in Manchester yesterday will have caused significant fear and concern in communities across the U.K., including here in London,” the force said in a statement Friday. “Yet at a time when we want to be deploying every available officer to ensure the safety of those communities, we are instead having to plan for a gathering of more than 1,000 people in Trafalgar Square on Saturday in support of a terrorist organization.”

The organizers, Defend our Juries, have insisted the march will go ahead.

“First let us say that we utterly condemn the attack on the Jewish community in Manchester,” the group said in a letter to Assistant Commissioner Ade Adelekan. “This is what genuine terrorism looks like and we join with others in condemning it unreservedly.”

The group said the government’s decision to restrict protests and ban Palestine Action have caused police resources to be stretched. “We urge you therefore to choose to prioritize protecting the community, rather than arresting those peacefully holding signs in opposition to the absurd and draconian ban of a domestic direct action group,” the letter said.

“As I’m sure you will understand, the protection of our democracy and the prevention of countless deaths are critical issues. Therefore, our protest will go ahead as planned for this Saturday.”