[5] Kostopoulos worked at the "Athens Check Point", and volunteered with the Positive Voice—an association of HIV-positive people of Greece—writing articles on the internet and for newspapers.

Kostopoulos was killed on 21 September 2018 at Gladstonos Street in the center of Athens,[10][11][12] and was buried in the town of Kirra where he grew up.

[14] Initial Greek media reports said that Kostopoulos was a drug addict who was committing a robbery of the jewelry shop.

Forensic Architecture found that the police had overlooked twelve cameras that were recording the scene and failed to question a key witness who appeared in the footage.

[14] Six people, including four police officers, the shop owner, and another man who was filmed beating Kostopoulos, were charged with inflicting "fatal bodily harm" causing death.

[9] The trial, that presiding judge Giorgos Kassimis described as "historic", was originally scheduled for October 2020, but was delayed due to the effect of the COVID-19 pandemic in Greece.

[26] The Mayor of Athens, Kostas Bakoyannis, responded with a counter-proposal to create a monument against intolerance, racism, and hatred, that the majority voted in favor of.

[27] In 2021, a researcher at Aristotle University of Thessaloniki named a newly discovered species of cyanobacteria, the Iphianassa zackieohae, after Kostopoulos.