Police beat up angry relatives who say they aren't investigating the 17-year-old factory worker's death.
Du Yanlin felt he 'should definitely do something' to mark the anniversary of the massacre.
The move comes after an investigative journalist exposes a surrogate test-sitting syndicate.
The news emerges as China lauds its own 'tremendous' human rights record, and as a key women's rights group is forced to close.
Netizen comments on Chinese news sites welcome the alleged attack as a sign of China's growing power.
Police swoop on anyone posting online about the crackdown, which is a banned topic in mainstream and social media.
Relatives say they have been prevented from getting near the cruise site, where workers have begun to right the upturned cruise ship.
Organizers of this year's 26th anniversary vigil say the event is now strongly linked to the city's Umbrella Movement last year.
Petitioners hope the anniversary of the June 4, 1989 bloodshed will boost their cause, amid tight security around victims' relatives.
Relatives of passengers hit out in frustration at security restrictions and a lack of official information.
The law, if passed, will bring nongovernment groups under the aegis of the state security regime and cut off overseas funding, activists say.
Relatives say they have heard nothing from officials, who say they are doing all they can to support them.
Former top Communist Party aide Bao Tong is taken 'on vacation' by state security police.
Activists brush aside reports of deep divisions among the city's students ahead of a public candlelight vigil.
The live-fire exercises come amid rising tensions in the border region after the fighting spilled into China.