Reading the Wikipedia entry about the Tienanmen massacre, it seems that that cable is completely unreliable. While Western estimates of the number of victims is now of about three thousand at most, decade long efforts in China to locate the victims' families has only managed to count about 200, more or less consistent with China's official numbers.

Also, apparently, there was no massacre in the square itself, which was evacuated by military mostly in anti-riot gear.

https://en.m.wikipedia.org/wiki/1989_Tiananmen_Square_protes...