It's a common method to raise small Angels with the likes of smaller fish to have them think of the other fish as "friends, not food" ( Sorry, watched Nemo the other day
) but that doesn't work 100% of the time. Hunger plays a strong influence on that situation. One of my ex business partners raised some Discus in a tank with 100 cardinal tetras. He said that it was a sight to see when the school of cardinals would swarm over the discus as they went from one place to the other in the tank. They were together for over a year with no predation. He had to go away for the weekend and thought it fine to just put some live worms in a cone feeder to feed the fish while he was away. He said when he returned, just 3 days later, almost 1/2 of the cardinals were gone. Guess there wasn't enough worms for them.
In your case, the fish in the tank may have been "safe" but did you try to add other smaller fish after the Angel(s) were large enough to eat them? Just curious how that went.