How the experts are helping Torontonians deal with the psychological impact of the van attack

It's a type of public coming together that experts say can be healing.

People showing up at the site in tears, leaving a note or flowers, sometimes standing side-by-side with strangers also dealing with shock and helplessness in the face of a senseless act of violence that left 10 people dead and another 14 injured.

"This is actually a really positive sign, being part of something like that, whether it's in person or online," said Walter Callaghan, a PhD candidate in medical anthropology at the University of Toronto who studies Post Traumatic Stress Disorder (PTSD) in military veterans.

Callaghan says many people, not just those who witnessed the crash or have a connection to one of the victims, could be experiencing symptoms such as nightmares, flashbacks or anxiety in public places.

The good news, he says, is that for most people, it's temporary.  

"For most people, by the end of the week they should come back to normal," Callaghan said, particularly if they have a strong social support network, whether those connections are online or in person.

While people may worry they have PTSD, he says that diagnosis is uncommon and only comes following at least a month of severe symptoms.

"If they've got nightmares every single night ... being so anxious and full of fear when they walk down the street, if the sight of a van causes them to panic, that's the time to definitely seek professional, clinical help."

The non-profit charitable agency Victim Services, which supports victims of crime, is providing immediate crisis help for anyone who needs it, hoping to ward off more serious psychological impacts.

"What we're seeing a lot of right now is shock and disbelief," Bobbie McMurrich, the group's associate executive director, told CBC Toronto Tuesday.

McMurrich says witnesses and family members of victims are among those receiving support.

"People are overwhelmed, they're terrified, so our role is to really bring a calming influence to that environment."

In the first 24 hours after the crash, McMurrich says her agency assisted 100 people.

McMurrich expects after these first days, people will begin to feel anger and grief, in some cases, only once the funerals happen.

Like Callaghan, she says strong social supports are key to helping people recover.

She says her teams will help everyone. 

"It can be very difficult, but we don't allow waiting lists... we actually make it work for everybody."