But as the hour grew later — and the bar tab bigger — the politics that have buffeted the office for months suddenly intruded on the evening, people who were there recounted later. In a quiet corner, away from the charcuterie and veggie dip, Jonathan Hornok, a top aide to Jeanine Pirro, the Trump appointee picked to run the office, was firing Jon Hooks, a senior prosecutor who had worked there for nearly 20 years.