Mark 3:13-19

And he went up on the mountain and called to him those whom he desired. and they came to him. And he appointed twelve (whom he also named apostles) so that they might be with him and he might send them out to preach and have authority to cast out demons. He appointed the twelve: Simon (to whom he gave the name Peter), James the son of Zebedee and John the brother of James (to whom he gave the name Boanerges, that is, Sons of Thunder); Andrew, and Philip, and Bartholomew, and Matthew,  and Thomas, and James the son of Alphaeus,  and Thaddaeus, and Simon the Canaanaean, and Judas Iscariot, who betrayed him.

These were the 12 representative disciples.

They were men of Galilee, and conversed with Yeshu in the Galilean dialect. For three years they accompanied him everywhere. They were not highly educated; but they did preach, and they also healed and cast out demons.

The Twelve followed him until his betrayal and arrest. At the arrest they ran away in fear.  The betrayal is described by Mark as though he had been present there himself to see it (See Chapter 14).