I Thought These were Pacu until I saw their Teeth! (Wild Piranha?) Fly Fishing Miami FL

I was riding my bike while Fly Fishing in Miami and I came across this pond. I noticed one strange looking fish and thought wow, I've never caught a Pacu and tossed my fly at him. It charged it like a Piranha and had jagged teeth much like a Piranha. Their behavior was also not Pacu-like being that they were in a pack and feeding frenzy.

These were likely very hungry Pacu that were willing to eat flies that mimic other fish, while Pacu are actually vegetarian fish.