Criminal Sentence 56: Em Dash or Colon?

From something I recently read for a client:

"We have several core competencies—they are"

I often see em dashes used incorrectly, especially instead of a period. The main use of an em dash is to initiate a break in thought:

"He asked me out—I couldn't believe it—and I gladly accepted."

So, above it would be better to use different punctuation:

"We have several core competencies:"