Nack's last line pretty much says it all.
Nack Springing into action. Sorry, had to say it.
hey, thats pretty much what I would said would happen, while SA-X is firing at Samus and Chrono he shoots her in the back, and if she's not killed by that she'll turn around to deal with him and get shot in the back AGAIN by Samus and Chrono.
Treachery 101, double-crossing someone while seemingly double-crossing someone else is a very effective way of getting what you want or accomplishing your mission.
BOOM headshot! XD