There have been plenty of books on the subject by people who has escaped China during this time.

Students and later supporters were shot at or ran over by tanks if they refused to leave. This was in a time when China would publicly execute you if you were homosexual or if you were a female that had too many boyfriends. Then they opened fire on bystanders watching from the side lines.

Soon after the initial murders happened riots by bystanders started. Heavy casualties were reported by several sources. China estimated several hundred while other media reported several thousand.

Reports from survivors state friends who were shot would be thrown in the streets to be crushed by tanks or bulldozers and the viscera hosed down drain systems. Survivors claim victims families were sometimes charged with reimbursement for the bullets used on the deceased.

The June 4th incident is still whispered heavily today by the Chinese people. The only people that deny it are tankies.

Most of this can be verified though pictures, documents and video footage.

The only involvement by the CIA was though Operation Yellowbird on helping the protesters escape though Honk Kong.