RCMP security detail put their hands up to protect Liberal Leader Justin Trudeau as protesters shout and throw gravel while leaving a campaign stop at a local microbrewery during the Canadian federal election campaign in London Ont., on Monday, September 6, 2021. THE CANADIAN PRESS/Nathan Denette

OTTAWA - Police in London, Ont., say they are investigating after someone threw gravel at Liberal Leader Justin Trudeau during a campaign event Monday.

A spokesman for the police service in the southwestern Ontario city said they are asking the public for information about the incident.

Trudeau told reporters Tuesday he felt the gravel hit him but was not hurt, and he will leave it to the police to determine what should happen as a result of the incident. The stones not only struck Trudeau but also some members of his RCMP protective detail and journalists covering the campaign.

"Let me be very clear and state the obvious — first and foremost, it is absolutely unacceptable that people be throwing things and endangering others at a political rally," Trudeau said at an event in Montreal.

He was there to discuss the Liberals' plan for housing, but spent most of the news conference instead answering questions again about the security of his campaign. He said there will be conversations about ensuring campaign events can be done safely.

In response to questions from The Canadian Press, an RCMP spokesperson said their protective services detail is assigned to protect leaders, and local police are in charge of crowd control.

A London Police Service spokesman said updates on the investigation will be provided "as appropriate."

Trudeau said the harassment and intimidation and physical violence is not just happening at political rallies, pointing to similar incidents outside hospitals across Canada in recent days. He also said retail workers and restaurant staff have also been targets for abuse from anti-maskers for months.

While Trudeau's campaign has been targeted by anti-vaccine crowds from the outset, it's not just the leader's tour affected.

Calgary Centre Liberal candidate Sabrina Grover said two of her volunteers were assaulted when they were out door-knocking on Sunday.

Grover said an individual used the pamphlets being handed out by the volunteers to strike them and also spit in their faces.

"Spit on in the time of COVID, so you can only understand how distressing that is," Grover told The Canadian Press.

She said a police report was filed Tuesday, and the volunteers are shaken but otherwise OK.

"This is the first time any interaction that we've had has gotten physically violent but this hasn't been the first time we've experienced an increasing level of a negative interaction or hateful interaction," she said.

"It needs to be called out by every party, every leader."

Christopher Holcroft, founder of the Civil Dialogue Initiative, which aims to protect and strengthen Canadian democracy, said the recent events at hospitals and Trudeau's rallies are "extremely disturbing" and "dangerous."

"In Canada, we don't decide things based on who yells the loudest," he said. "In Canada, we certainly don't decide things by throwing rocks, and it's vitally, vitally important to the well-being of our democracy that citizens speak up now."

He said he is calling for rallies on Sept. 18 across Canada to show commitment to science and civic responsibility.

"We should begin to mobilize because we saw how it impacted the U.S. democracy, as one example, and I'm very concerned that if we as Canadians do not begin to speak out very clearly, very strongly, very passionately for issues like basic decency and civility, responsibility, respect for science and evidence, then we risk going down a similar path," Holcroft said.

Party leaders were united in their condemnation of the violence at the Trudeau event.

"There is never an excuse to intimidate people, to promote violence or to harass people, when in Canada we should have a healthy debate about the future of our country," Conservative Leader Erin O'Toole said at his Tuesday news conference at an Ottawa hotel.

"That type of conduct is unacceptable towards anyone."

NDP Leader Jagmeet Singh said the behaviour crossed a line, noting when someone throws a rock their intention is clearly to hurt someone.

"That is horrible and that's wrong," he said while taking questions from reporters in Toronto.

Singh's campaign stops have not seen the same kind of angry crowds but the NDP leader is regularly subjected to racist insults, including from people driving by his events who have hurled hateful slurs out their windows as they pass.

Bloc Québécois Leader Yves-Francois Blanchet said there is never an excuse to intimidate or be violent.

Annamie Paul, leader of the Green Party, has said previously her campaign has been targeted with racist attacks and threats on social media.

People's Party of Canada Leader Maxime Bernier also joined the chorus, even though the crowd at the Trudeau event was dominated by his supporters.

"Some idiot threw pebbles at Mr. Trudeau yesterday," Bernier tweeted. "I condemn it. Words are our weapons. But physical violence is always wrong."

Bernier pointed out, however, that someone smashed an egg on his head last week, and none of the other leaders were asked to comment on that incident.

It occurred in Saskatoon on Thursday, when a man posing as a supporter asked to have a photo taken with Bernier, and then hit him in the back of the head with the egg.

Some leaders are suggesting Trudeau must change how he is campaigning. Blanchet said if he went into hostile crowds like Trudeau has been doing, his RCMP security detail would frown at him. Singh said perhaps the location of events should be better chosen.

Trudeau said he will follow the advice of the RCMP on whether events can proceed or not. A Liberal rally planned in Bolton, Ont., on Aug. 27 was cancelled on the advice of the RCMP when it was felt safety could not be guaranteed.

This report by The Canadian Press was first published Sept. 7, 2021.

— With files from Paola Loriggio in Toronto and Maan Alhmidi in Ottawa

News from © The Canadian Press, 2021