With the beginning of the Holy Thursday Mass, we enter into the three holy days of the Easter Triduum. Taking place over three days, this one celebration starts on Holy Thursday and does not end until the Easter Vigil on Saturday. So after Mass on Thursday, there is no "end of Mass" we simply quietly leave and anticipate coming back for the next part on Good Friday. Subsequently, after services on Good Friday, we do not "end" but quietly leave anticipating our return the next day for the conclusion at the Easter Vigil.
On Holy Thursday, we celebrate the beauty and mystery of the Last Supper much like we do every Sunday. However, there is a sense in the air that there is something more we are called to remember - the Last Supper.
On this night we also participate in the washing of the feet. Just as Jesus humbly demonstrated with his apostles, we are called to remember who we are and what we are called to do as Christians, serve others.
After we have participated in the breaking of bread and have been reminded of our mission to serve others, we are not done. We are sent home with the intention of returning tomorrow for the final day of these holiest of days.