US mainstream news outlets like CBS News with actual reporters on the ground at the time: https://www.cbsnews.com/news/there-was-no-tiananmen-square-massacre/
Classified US communications with assets on the ground: https://wikileaks.org/plusd/cables/89BEIJING18828_a.html
Image Analysis
In one of the links listed by op:
"GALLO SAW MANY CASUALTIES BROUGHT INTO THE SQUARE AND DID NOT DOUBT THAT HUNDREDS OF PEOPLE IN BEIJING WERE KILLED BY THE ARMY ON JUNE 3 AND 4."
Yup. Sounds like a massacre to me.