But behold, I say unto you that if ye persist in your wickedness that your days shall not be in the land, for the shall be sent upon you; and if ye repent not they shall come in a time when you know not, and ye shall be visited with destruction; and it shall be according to the fierce of the Lord.
In Alma 10:22-23, Amulek says:
The people have been warned: If they don't repent, the Lamanites will visit them with utter destruction. It has not happened yet, only because of the prayers of the righteous. But if they cast out the righteous, the Lord will not "stay his hand".
What did the people of Ammonihah do? Alma 14:7:
And they spit upon him, and him out from among them, and also all those who believed in the words which had been spoken by Alma and Amulek; and they cast them out, and sent men to cast stones at them.Alma 15:15
But as to the people that were in the land of Ammonihah, they yet remained a hard-hearted and a stiffnecked people; and they repented not of their sins,Basically exactly what they were warned against.
What happened next? Alma 16:2-3
Basically, exactly what was prophesied