While true, this is after the army had already made its way into the area by opening fire on the protestors. The protesters, after being confined to the square, didn't see much point in resisting further, as their leadership fell apart and there had been plenty of casualties already. Right above the section you quoted:

At about 10:30 p.m., still being pummeled by rocks thrown by protesters, the 38th Army troops opened fire with live ammunition.[176] The crowds were stunned that the army was using live ammunition and fell back towards Muxidi Bridge.[176][179] The troops used expanding bullets,[11] prohibited by international law[180] for use in warfare between countries but not for other uses.[181]

The advance of the army was again halted by another blockade at Muxidi, about 5 km west of the square.[182] After protesters repelled an attempt by an anti-riot brigade to storm the bridge,[175] regular troops advanced on the crowd and turned their weapons on them. Soldiers alternated between shooting into the air and firing directly at protesters.[183][173][182] As the army advanced, fatalities were recorded along Chang'an Avenue. By far, the largest number occurred in the two-mile stretch of road running from Muxidi to Xidan, where "65 PLA trucks and 47 APCs ... were totally destroyed, and 485 other military vehicles were damaged."[37] Although troops advanced into Beijing from all directions, the majority of deaths during the night of 3 June occurred around the Muxidi area.[184][185][186][173][187][188]

Throughout the street fighting, demonstrators attacked troops with poles, rocks, and molotov cocktails; Jeff Widener reported witnessing rioters setting fire to military vehicles and beating the soldiers inside them to death.[189] On one avenue in western Beijing, anti-government protestors torched a military convoy of more than 100 trucks and armored vehicles.[190] They also hijacked an armored personnel carrier, taking it on a joy ride. These scenes were captured on camera and broadcast by Chinese state television.[191]

In the evening, a firefight broke out between soldiers and demonstrators at Shuangjing.[192]

Obviously this was far from a peaceful protest, with protesters attacking and killing soldiers after said soldiers were ordered to make their way to the square, and some of the protest leaders explicitly calling for bloodshed.

I don't know how I would've handled it personally, as I lack the cultural background needed to properly understand the cause of the protest, but it feels disingenuous to call the dispersal "peaceful". The fact that the government hides the official death toll also doesn't help their reputation.