[What you need to know to start the day: Get New York Today in your inbox.]

On the morning of the New York Police Department’s July crime briefing, the department’s highest ranking officer, Chief Terence A. Monahan, was frustrated.

For months, his officers had wrestled with a stubborn spike in gun violence in northern Brooklyn, and by Chief Monahan’s assessment, the statistics were not his department’s fault. He took the microphone and aimed a public swipe at Brooklyn’s district attorney, Eric Gonzalez.