More can be said but there are some decent previous answers on the nature of the Tiananmen Square massacre, and its meaning, discussing it from a variety of perspectives:
/u/yodatsracist answered I have a Chinese exchange student, and he would like to learn about the Tiananmen Square protests. What resources would you recommend for him to read?
/u/DeSoulis answered Why did Deng Xiaoping send in the tanks back in 1989?
/u/Spiritof454 answered This article claims that what happened in Tiananmen Square in 1989 has been purposefully mischaracterized by the west for propaganda purposes. Is that accurate?
Hope that helps!