John Gill Commentary Acts 9:30

"And when the brethren knew it, they brought him down to Caesarea, and sent him forth to Tarsus." — Acts 9:30 (ASV)

Which when the brethren knew
When the members of the church heard of it, by some means or another:

they brought him down to Caesarea ;
not that which was before called Strato's tower, the same as in (Acts 8:40) but Caesarea Philippi, mentioned in (Matthew 16:13) the Syriac version adds, "by night", and some copies, "and sent him forth to Tarsus"; a city of Cilicia, his own native place, where he might be more safe, and also useful among his friends and acquaintance; (Galatians 1:21) .