And 30 feet is further than most cross room shots add a choke (he was probably using a culinder bore) with a shorter distance and it can be devastating.From a Nevada Corrections Institute
About 30 feet away, another officer was manning the control room—a trainee named John-Raynaldo Ramos. His job was to remotely open the cell doors from "the bubble," the glass room overlooking the floor. The elevated booth is equipped with a 12-gauge shotgun loaded with 7 1/2-birdshot—the same tiny pellets that sport shooters use to blow apart clay pigeons and that hunters use to kill birds and rabbits. The windows of the bubble, which are reinforced with security bars, can be opened to aim a gun through. "Get on the ground," Ramos ordered the two men.
Ramos fired a warning shot, but the prisoners kept scuffling. Then he fired three live rounds. When he stopped, the left side of Arevalo's body was loaded with shots. Perez lay motionless and bleeding on the floor, near a shower bag and a towel. He had at least 30 pellets in his face, 30 in his neck and as many as 200 in his chest and arms. Ramos asked another officer, Isaiah Smith, to call the prison medical staff while he tried to reload his gun.
About an hour after being released from his cell, Perez was pronounced dead. Arevalo was taken to the University Medical Center of Southern Nevada in Las Vegas, where staff recorded that he had retained "extensive" shots to the "left face, left neck, left arm, left chest, left flank."
I agree hi base 4 shot would be a better choice. The guards were using 7 1/2 shot. Possibly like trap loads. I wouldn't recommend that.