MANGALDAI, June 21: The Orang National Park (ONP) authorities promptly swung into action following the killing of a full grown female rhino in the evening of June 20 and arrested two hard-core poachers at Jakhalabandha in Nagaon district, at a distance of about 140 km from ONP, while they were proceeding towards Dimapur, Nagaland, in a passenger bus today at about 9 am.