Watching the livestream of the brutal slaying of 50 people at mosques in Christchurch would have had a huge psychological impact on those who stumbled across it on social media and those who used it in their search for loved ones, experts say.
With the traumatic footage shared so many times on Friday, many people would have come across it online and watched it before realising what was going on.
New Zealand Association of Counsellors president Bev Weber said people may not have felt the impact at the time if they did not realise what they were watching but believed it would be "very, very traumatic" for them.
Canterbury executive member of the NZ Association of Counsellors Christine Macfarlane agreed seeing the footage could contribute to the trauma people were already facing.
"They are not going to forget what happened. You can't unsee what you've seen."
Those people who stumbled across the footage should eat well, get plenty of sleep, seek support from family or friends, talk about it and stay around people, she said. Drawing your feelings could also be useful when language was too hard.
Clinical psychologist Dr Neil Thompson agreed there was the issue of "vicarious trauma" for those who saw the footage but weren't directly involved.
"Many people will have been sent and accessed this material at a time of crisis and uncertainty when information about the events was scant. To this end many people may have found themselves looking at material that in other circumstances they may have decided not to view," he said.
"It is important that individuals who have seen this material seek help if the content has disturbed them."
Stories had also emerged of desperate family members watching the footage to try to find out what happened to their loved ones.
While it may have been the only option at the time, the "graphic pictures and the pain of watching someone you know be killed will always stick with them," Macfarlane said.
"As they are saying goodbye to family and friends and doing everyday life, those pictures will pop into their head."
Weber agreed it would be traumatising.
"It's the longer-term impact. What everybody's experiencing now is that they are still in the crisis situation. It will take a while for them to come to the realisation that they are not doing very well," Weber said.
Clinical psychologist Dr Neil Thompson said the livestream would be most traumatising for those who saw loved ones murdered or injured.
"It is understandable that in needing information about their loved ones that they would watch livestreams to find out what they can. For some, this may have given them a sense of control in a chaotic situation," he said.
"For others, it could be harrowing to see a loved one injured or killed and be helpless to prevent it. The long term effects are likely to be mixed, depending on how a person processes and makes sense of what they have seen."
If in a month people were still repeatedly re-experiencing the trauma, struggling to leave the house through fear, or having difficulty visiting specific places that reminded them of the events, they should seek professional help, he said.