I previously wrote about this in an answer to a slightly different question. This answer in turn links to several answers with more detailed discussion of the casualty estimates.

The consensus is that probably about a dozen deaths occurred in the square itself, with most of the killing happening around the Muxidi Bridge.

As with almost every aspect of the protests, there are conflicting eyewitness account. Some protest leaders and foreign observers in the square saw no violence or casualties. Though the square itself is huge, so this is not all that surprising.

Also keep in mind that the historical picture of events in Beijing is murky, and even less is publicly known about the level of violence involved in suppressing the concurrent large protests in dozens of other Chinese cities.

It is true the majority of deaths happened outside the Square; the roads leading to it (Fuxing Road, Fuxingmen Avenue, West Chang'an Avenue) were the most deadly. As troops rolled towards the Square some civilians wanted to try to stop their advance; some were just curious; some were not even trying to leave their homes but died anyway. And of course once word spread of the troops killing civilians, some people armed themselves -- with kitchen knives, daggers, or nothing at all, and tried to face the troops.

Part of the confusion with the events of the Square itself is when the "clearing" happened. The CCP sources claim lights were turned off at 4 am (this is verified by witnesses) and that the actual clearing happened at 4:30 am. However, prior to this, both the 38th Army and 15th Airborne tried to close off the square from anyone entering in (around 1:30 am) and the time prior to 4 am is when we have definite records of some people who died.

Dai Jinping: a master's student at the Beijing University of Agriculture. Was at the Square with a camera, and was shot at Mao Zedong's masoleum; he was taken to a hospital but died during surgery.

Li Haocheng: undergraduate at Tainjin Normal; taking photographs at the Square. He was hit by two bullets, and died at Tongren Hospital.

Cheng Renxing, Zhou Deping, and Huang Zinhua -- all graduate students -- were also shot and died during the same time, before the "official clearing" started.

There was also a moment where the student tents were driven over by APCs, and there are multiple accounts of some still within the tents; while the official account claims the tents were checked, Robin Munro testifies

We clearly saw that the advancing infantrymen walked behind the tanks.

That is, the tanks advanced ahead first, meaning there is no way the tents could be checked.

Additionally, while some protesters did eventually leave, a core group had resigned themselves to stay, and even the official CCP account indicates violence, that there were "students who insisted on not moving" so troops "compelled them to depart." We have accounts of students being trampled and clubbed. It is difficult to swallow with this level of violence that none of the students suffered fatal injuries, although there has been no definitive evidence in this respect.

...

Brook, T. (1998). Quelling the People: The Military Suppression of the Beijing Democracy Movement. Stanford University Press.

Brown, J. (2021). June Fourth: The Tiananmen Protests and Beijing Massacre of 1989. Cambridge University Press.