India: What were these violent clashes in Mathura between Azad Bharat Vidhik Vaicharik Kranti Satyagrahi and the police ?

Mathura clashes: Toll climbs to 21, probe ordered
TNN | Jun 3, 2016,

MATHURA: At least 21 people, including an SP and an SHO, have been killed in the massive clash between police and encroachers that broke out here on Thursday even as Uttar Pradesh chief minister Akhilesh Yadav has ordered an inquiry.

http://timesofindia.indiatimes.com/india/Mathura-clashes-Toll-climbs-to-21-probe-ordered/articleshow/52566146.cms