At the time when Mattathias and his sons fled to the mountains, many other Jews had fled to the wilderness to get away from Antiochus' decrees. The Maccabeans were one of them.
The Maccabeans were a group of pious zealots who had fled their homes to learn Torah. Mattathias became their leader and gathered more people who were willing to fight against the reign of Antiochus. Mattathias convinced the Maccabeans to defend themselves on the Sabbath.