What kind of massacre exactly happened?

The army gunned down mostly workers, Peking locals, who tried to stop them from advancing to the square by blockading the streets. More or less the same people who had previously handed out noodles to the troops to have an opportunity to tell them that those are Dengist students wanting some more reform, their sons and daughters, not violent reactionaries, to make sure that what the party hardliners told the army wasn't the only thing the soldiers knew. Which was a good thing because if the soldiers hadn't known they probably would not have reacted with as much restraint -- but they still followed orders and advanced to the square, leaving corpses in their wake.

The official party line is still, more or less, "If we hadn't cracked down there would have been murder and rampage" -- nope. The violence happened because significant parts of the party wanted to backstab Deng's reforms and definitely didn't want to set precedent that some students could just show up and protest and get party members to talk to them and negotiate -- which very much happened on the part of the reformist faction.

But I wouldn't be surprised that it's kinda inconceivable in the first place for a tankie that the Chinese party had, or has, factions. Their performance has been rather spotty when it comes to centralism, but it was certainly increased after Tiananmen, and also after the collapse of the USSR. Mostly though it's politics as usual.

How, exactly, is any of this "pro-CIA"? Are you just throwing out random accusations? And yes I'm an Anarchist. I always was, and always will be, anti-tankie. Deal with it. But I also know just a tad bit more about Tiananmen than your ordinary westerner or, for that matter, your ordinary tankie.