Caps of order 3q2 in affine 4-space in characteristic 2

We prove that a class of q-ary dual BCH-codes in characteristic 2 produce caps in AG(4,q). This is the first family of caps of order 3q^2 in PG(4,q). It is proved that our caps are complete in PG(4,q). We determine the weight distribution of the codes generated by the caps, via a close link to the binary Kloosterman codes, the dual Melas codes.