The people stood beholding (histēkei). Past perfect active of histēmi, intransitive and like imperfect. A graphic picture of the dazed multitude, some of whom may have been in the Triumphal Entry on Sunday morning.
Scoffed (exemuktērizon). Imperfect active, perhaps inchoative, began to turn up (out, ex) at the dying Christ. The language comes from Psa 22:7.
The Christ of God (ho Christos tou theou). He had claimed to be just this (Luk 22:67, Luk 22:70). The sarcastic sneer (he saved others; let him save others, for himself he cannot save) is in Mar 15:31; Mat 27:42. Luke alone gives the contemptuous use of houtos (this fellow) and the fling in “the elect” (ho eklektos). These rulers were having their day at last.