Not likely that any raptor would fly off with the chicken. A big redtailed hawk would weigh 3 1/2 lbs and would be capable of carrying off prey up to about 30% of her bodyweight (in hawks, owls, eagles, vultures, etc the female is always the largest). Elise, the redtailed hawk I work with, is right about 5 lbs and may well be the world's record fattest redtail in captivity, but she was raised on hotdogs, raw hamburger, and bologna by the halfwit bonehead that stole her from her nest 24 yrs ago. Calculating 30# of her bodywieght leaves you with 1.5 lbs of live chicken weight, mighty tiny chickens. Typically when a raptor kills something like a chicken (or grouse, pheasant, duck), they eat it right on the spot.
Betting it was a ground predator; fox, skink, coyote, chupacabra, etc that scattered the flock.
Try the trailcam trick to find your culprit. With the photos on the trailcam, the state Game/Fish guys can help you with trapping. You can bet once the local predators find an easy source of food they will be back for seconds. Prolly explains why lil red rooster was upset and wouldn't crow for days.
