The murder of Manny..
Was this too abrupt and impulsive even for Tony?
You had to expect Tony to be pissed. The fact these two were carrying on behind his back in secrecy was no small thing. Manny had to expect the shit to hit the fan.
I think there were some good story opportunities missed here. Tony stews over time thinking he cannot trust Manny any longer. Manny grows to fear Tony and not trust him. Perhaps he eventually orders Manny's execution being careful so his sister does not suspect that he was behind it. Make it look like a rival gang hit.
I just think it is too over the top to have Tony just start shooting as soon as he realizes the 2 of them are together.