I know that because they're the only ones facing the CSF with force while singing their hymns. eSocialists posts this video and adds Video Temporary withdrawal of CSF from Tahrir Square in the direction of Talaat Harb Square after forcefully breaking up the sit in Sharif Kouddous notes

At the end, they made the people believe that they would end the clashes and allow the peaceful protest to continue until the Central Security forces with the rapid deployment forces attacked the youth after the people calmed down.