Almost all these magnificent buildings were used for ordinary theatrical performances during the 5th century. All of them, however, contain elements which are evidence that the orchestrae were not only used during musical or histrionic events but also for gladiatorial combats and hunts, which were a merciless way of eliminating huge numbers of Christians. […] Execution was performed in public, in the arenas or ochestrae of the amphitheatres and theatres, and was particularly common during the reigns of Nero, Trajan Decius, Diocletian and other of the Roman emperors.
Source: wiktionary