Before you get downvoted by the tankies, note for historical accuracy (so that I will be downvoted because they like that even less, OTOH lemmygrad doesn’t even see me so w/e): The massacres were in side streets, not on the square itself. The party was at first split as to how to deal with the protests, the students were to simplify quite a bit Dengists alarmed by the power shifts within the party away from Dengism following Hu Yaobang’s death. Hardline faction was amassing the army outside of Peking, Peking locals went out there and handed them noodles and explanations as to the situation, explaining that the protesters were their sons and daughters, good socialists¹, not some bourgeois anti-revolutionary mob. Dengist faction lost out in the internal party struggle, hardliners decided that the army shall march, army marched, Peking locals erected barricades etc. in the streets leading to the square, get massacred, army arrives at square, delivers final ultimatum, students retreat, with no further or at least minimal bloodshed.

¹ According to Marxist-Leninist-Maoist type thought. People understanding actual theory understand that Dengists are even more capitalist than Lenin, but MLs never acknowledge that state capitalism is, indeed, capitalism, and Dengists never acknowledge that they’re not even doing state capitalism any more but run of the mill oligarchic capitalism.