Five years ago today, an Islamic State suicide bomber blew himself up at a cultural center in Turkey’s southeastern border town of Suruc. The attack killed 33 civilians, the first in a wave of bloody jihadi attacks against Kurdish activists and their allies inside Turkey. Families of the victims say justice has yet to be served.

Seyh Abdurrahman Alagaoz killed himself along with the tens of idealistic youths who had arrived from across Turkey. They were planning to carry toys, medical supplies and other materials to Kobani, the mainly Kurdish Syrian town directly across the border from Suruc that was reduced to ruins in a bloody standoff with IS.

Families of the victims held separate gatherings in Suruc, Istanbul and Ankara to commemorate the tragedy. In Suruc, police backed by armored vehicles and water cannons threatened to intervene when families went to unfurl posters of the deceased.

At a joint news conference in the city of Urfa, lawyers for the victim’s families said authorities had refused to cooperate from the get-go, part of what they charge is an ongoing effort to shield the perpetrators. They presented evidence of the government’s alleged cover-up in a report.