That people were killed in Tiananmen Square itself, that the soldiers were the first ones to kill, and that the death toll was something like 10,000. It gets played up on Reddit because of red scare propaganda and plain old chauvinism.

I wasn't going to say that at first [simply because it's a bit obnoxious] but since other people are courting drama and I was collecting links from another conversation so it's convenient to do, so I'll repost them here:

There was a great deal of violence and many students (along with other protestors, as well as the militants and soldiers) died, so I'll mark each link with an appropriate content warning, though that's mostly because the last one is rough, while the ones before it are unlikely to cause people issues.

First, here are video interviews with some of the former student leaders, the first one with Chai Ling actually being before the incident took place. There is some gunfire and yelling that a western news program uses for "ambience", but nothing is shown. Chai Ling describes a bloody scene, though that specific scene is patently fictional (this is established by the others who are interviewed).

Next is an article which discusses the subject, partly quoting student leaders above. It describes violence in broad strokes but doesn't have any pictures. It also talks about statements made by a British reporter who was there.

Third, here is secondary reporting leaked on documents from the US Embassy in Beijing and the actual report from a Latin American diplomat that was leaked. The latter revealing contains in its summary: "ALTHOUGH THEIR ACCOUNT GENERALLY FOLLOWS THOSE PREVIOUSLY REPORTED, THEIR UNIQUE EXPERIENCES PROVIDE ADDITIONAL INSIGHT AND CORROBORATION OF EVENTS IN THE SQUARE." (source text is all caps). There is very little description of violence, just mention of gunfire being present, people being wounded, etc.

{Caution} Lastly, here's an article written arguing that the event is misrepresented in mass media. I link it mainly because it includes photographic evidence that is very difficult to argue with for reasons beyond it being difficult to look at. Graphic depiction of stripped corpses of soldiers that were strung up after death.

Obviously there's more than this, but these were the links I collected recently. Chai Ling says things that are even more unhinged in footage I think they excluded from that excerpt of the interview.