For the previous 94 minutes, a number of Celtic fans had reveled in taunting their Italian hosts, particularly after a similarly heated game in Glasgow between the clubs a fortnight ago.
Shortly after Lazio's arrival in Glasgow on October 24, videos appeared on social media seemingly showing Lazio "ultras" -- a hardcore faction of supporters -- making fascist raised-arm gestures as they walked through the city center.
During the Glasgow game, the Celtic fans unfurled a banner with an image of Mussolini hanging by his feet and the message "Follow Your Leader."
This prompted Mussolini granddaughter Alessandra Mussolini to call for Celtic fans to be prosecuted.
On the eve of the game, Celtic confirmed that two of its fans had been stabbed in Rome.
Ahead of the game in Rome, Celtic had advised its fans to stay in large groups where possible, keep a low profile in the city and avoid wearing club colors.
European football's governing body UEFA said their "disciplinary body will await reports from last night before deciding on any action."
For many Celtic fans, the opportunity to travel to Rome was both a sporting and religious pilgrimage.
Because of financial difficulties, many Irish Catholic emigrants moved to the east end of Glasgow, with many of them becoming Celtic fans.
As a result, the Irish tricolor can often be seen as Celtic take to the field in Glasgow.
Pictures from Thursday's game showed Celtic fans carrying Vatican City flags, and banners adorned with Pope Francis' face were commonplace.