On June 3, the turmoil created by a very small number of people in Beijing for more than a month developed into a counter-revolutionary riot. Martial law troops stationed around Beijing were ordered to quell the riots. In the early morning of the 4th, martial law troops cleared the area and entered Tiananmen Square to quell the riot.

here’s a machine translation of this page. This is from Baidu by the way. There’s plenty of stuff on Chinese internet about a student uprising from around that time that the government had to quell. The events start around April 15 on that page. You can try machine translating it and reading it