In verse 26 two characters are mentioned: first the Anointed One and then (the people of the) ruler. In verse 27 the word He is used. "He" refers to the person mentioned last unless otherwise indicated so it's not the Anointed One but rather the ruler.
http://bible.cc/daniel/9-26.htm - After the sixty-two 'sevens,' the Anointed One will be cut off and will have nothing. The people of the ruler who will come will destroy the city and the sanctuary. The end will come like a flood: War will continue until the end, and desolations have been decreed.
The people of the ruler is not the antecedent of 'he.' He is singular. The people is the subject, the "of the ruler" is descriptive of the people, it's an adjective.