Mr Chen felt "awkward" as they took the snap, but he didn't want to cause a scene. Later, he asked colleagues if they had ever had the same experience - no-one had. "So it was just me, literally. It was clearly some sort of security procedure the guards were enforcing. They didn't offer any explanation."
The department told the BBC its security protocols were "agnostic of background or ethnicity". Mr Chen suspects that was not true in his case. He is among many Chinese-Australians who feel they are facing increasing scrutiny and suspicion - solely based on their heritage - as Australia hardens its views towards China.