Prime minister Malcolm Turnbull has promised a royal commission into the Northern Territory corrections system after shocking footage emerged of boys being physically mistreated at one of the centres. ABC Four Corners ABC's Four Corners aired the vision last night from inside the Don Dale detention centre, which included images of teenage boys being sprayed with tear gas while being held in isolation and transported in hoods and restraints.On Tuesday, Malcolm Turnbull called the actions "shocking" and said there would be a "swift inquiry" into the corrections system in the Northern Territory."We will get to the bottom of this swiftly and we will identify the lessons that need to be learned," Mr Turnbull said."We have here a very troubling state of affairs where clearly there has been mistreatment of young people."Turnbull has spoken to human rights commission president Gillian Triggs who said that she has never seen that kind of treatment seen in the program in Australia before.It's not the first time that shocking events in the Don Dale detention facility have come to light. A report was released in September last year which detailed the gassing of boys at the centre.