Detective Chief Inspector Cath Cummings said: "We understand the concern that such a serious incident will cause in our communities, especially given the young age of the victims.
"At this early stage, I would urge anyone with information to make themselves known, either to officers in Westvale this evening, or by reporting to us directly or via Crimestoppers.
"I’d ask that anyone who saw the incident, was passing or lives nearby shares what they know so we can establish what happened and find those responsible.
"There will be a significant police presence in the area tonight as we carry out this vital work, and we are speaking to local businesses and residents to gather information. If you know anything, do the right thing and come forward."
