So, what happened after, when the cameras weren’t looking? We don’t really know. To the Wiki (footnotes omitted):
The government of the People’s Republic of China has made few statements about the incident or the people involved. In a 1990 interview with Barbara Walters, then-CPC General Secretary Jiang Zemin was asked what became of the man. Jiang first stated (through an interpreter), “I can’t confirm whether this young man you mentioned was arrested or not,” and then replied in English, “I think…never killed” [sic]. At the time, the party’s propaganda apparatus referred to the incident as showing the “humanity” of the country’s military.
In a similar vein, Anderson points us to this New York Times story about divisions within the Chinese military leadership at the time. The Times reporters, Andrew Jacobs and Chris Buckley, point in particular to the story of one general, Xu Qinxian:
In a stunning rebuke to his superiors, Maj. Gen. Xu Qinxian, leader of the mighty 38th Group Army, said the protests were a political problem and should be settled through negotiations, not force, according to new accounts of his actions from researchers who interviewed him.
“I’d rather be beheaded than be a criminal in the eyes of history,” he told Yang Jisheng, a historian.
Although General Xu was soon arrested, his defiance sent shudders through the party establishment, fueling speculation of a military revolt and heightening the leadership’s belief that the student-led protests were nothing less than a mortal threat to the Communist Party.
The overall picture that emerges from the Times article is one of Army officers expressing reluctance and reservation, rather than outright defiance: “The interviews and documents show that even at the time, few in the military wanted to take direct responsibility for the decision to fire on civilians. Even as troops pressed into Beijing, they were given vague, confusing instructions about what to do, and some commanders sought reassurances that they would not be required to shoot.”
Still, to the political leadership of the PRC at the time, I’m sure that reluctance and reservation were quite terrifying, coming from the men who controlled the men with the guns.
As for Xu: “In the end, General Xu agreed to pass the orders to his officers, but not to lead armed troops into the capital. He was arrested, expelled from the party, and served four years in prison, Mr. Yang said.”