"And when" on the second verse is not reffering to an event that comes afterward, but moreso only referring to an event which happened. In some other translations the "And when" is translated as "In the meantime".
So... "when they feared the consequences thereof and saw that they had gone astray" was at the same time Moses came back. They aren't separate events. They feared the consequences and saw that they went astray at the time Moses came back. It wasn't at their own conscience. The following verse even states...
"And when Moses returned unto his people, angry and grieved, he said: Evil is that (course) which ye took after I had left you. Would ye hasten on the judgment of your Lord ? And he cast down the tablets, and he seized his brother by the head, dragging him toward him. He said: Son of my mother! Lo! the folk did judge me weak and almost killed me. Oh, make not mine enemies to triumph over me and place me not among the evil-doers."
Hence you can see Aaron (Moses brother) failed in trying to get them to repent in Moses' absence.
They aren't separate events, they have never been believed to be separate events, nor is there any reason to believe so. The other verse compliments the verse, rather than contradicts it.(BowOfHak)