In the first 24 hours after the attack, Facebook took down 1.5 million videos of it but has admitted there may still be more out there being uploaded.
Many adults would be surprised at just how easy it is to watch, Wood says.
"Adults are aware of Facebook, but I think they are less of how the kids tend not to use Facebook and they tend to use Instagram and Snapchat for quick posts. I just think adults are unaware of that culture."
He says students with the freedom of access and ability to roam, almost certainly would have had some sort of contact with the video.
He believes the solution is not a "punitive" one, but rather about coming down to their level and helping them figure out a potential loss of innocence.
Child psychotherapist Joanne Bruce encouraged parents to initiate conversations with their children and use "simple language and just go with the emotions".
Clinical psychologist Maren Klum said it was important for people who were feeling overwhelmed to ask for help.
"It is a grieving process," she said. "Talk to your families, loved ones and friends rather than internalising it."
Ministry of Education secretary for education Iona Holsted said traumatic incident support had been offered to all schools, kura and early learning services following the tragedy.
"This is a really tough time for New Zealanders and it's critical our children and young people get the support and care they need as they return to schools and other learning institutions," she said.
Additional traumatic incident teams were on standby across the country and tips on supporting conversations with children and teenagers had been circulated to all schools.
The Ministry of Health has also developed resources, available in different languages, to assist those in mental distress as a result of the Christchurch tragedy.
Parents and teachers can help children and young people feel safe by:
- Providing reassurance and keeping to routines
- Staying calm and promoting a calm environment
- Doing enjoyable things together
- Taking time to listen and talk
Source: Ministry of Education
Where to get help:
- 1737, Need to talk? Call or text 1737 to talk to a counsellor (available 24/7)
- Lifeline: 0800 543 354 (available 24/7)
- Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
- Youthline: 0800 376 633, Kidsline: 0800 543 754 (available 24/7)
- Whatsup: 0800 942 8787 (1pm to 11pm)
- Depression helpline: 0800 111 757 (available 24/7)
- Rainbow Youth: (09) 376 4155
- Samaritans 0800 726 666
- If it is an emergency and you feel like you or someone else is at risk, call 111.