That is 1000% a Nazi salute being given behind the presidential podium on Inauguration Day (also MLK day) by the richest person on the planet. That moment will live in infamy.
That was one big performance by the NYPD and it backfired spectacularly. Their goal was to make Luigi Mangione look like a Batman villain. Instead it made him look like a folk hero who fought back against the system that puts profits over our own lives.