Mark 10:32-34

³² Now they were on the road, going up to Jerusalem, and Jesus was going before them; and they were amazed. And as they followed they were afraid. Then He took the twelve aside again and began to tell them the things that would happen to Him:

³³ “Behold, we are going up to Jerusalem, and the Son of Man will be betrayed to the chief priests and to the scribes; and they will condemn Him to death and deliver Him to the Gentiles;

³⁴ and they will mock Him, and scourge Him, and spit on Him, and kill Him. And the third day He will rise again.”

Also found in Matthew 20:17-19 and Luke 18:31-34 (in which we learn that the twelve understood none of what He said).

We have a construction in the Greek text which speaks, not of a momentary going on ahead but of an habitual practice. Jesus often walked alone, ahead of His disciples. … The Lord walked in advance of the Twelve with a solemnity and determination which foreboded danger. His manner struck awe into the minds of the Twelve. The words “as they followed,” do not refer to the disciples, but to the accompanying crowds, the travelers going tin caravan to Jerusalem. The Greek text has, “and those who followed.” The crowd who usually  hung upon the Lord’s footsteps, or His fellow-travelers on their way to the Passover, were conscious of a vague fear. … These feelings must have been awakened by the manner of Jesus, as of one laboring under strong emotion. … Filled with the varied feelings excited by [His] sacred recollections and tragic anticipation, He walks alone by preference, step and gesture revealing what was working within and inspiring awe. — Wuest, pages 208-209.

He took the twelve aside (v.32) — more support for the interpretation that Jesus walked ahead, followed by the twelve, who were, in turn, followed by a crowd.

happen (v.32) = “to come together,” of things that happen with one another

For the first time it is made clear that both Jews and Gentiles are to have a hand in [Jesus’ death], the Jews to condemn and the Gentiles to execute. The latter, had the disciples understood it, is tantamount to a disclosure that His death would be by crucifixion. Matthew (20:19) so records it. — Guthrie, page 873.