The hammer on Wade's rifle is down as he waits for the Lakota war party to close in. In the next scene, the hammer is back when he gives the command to fire.
The series is supposed to be taking place in 1883, yet the wagon train is attacked by free ranging Lakota. By 1883, the Lakota had been beaten down and were restricted to and controlled on reservations. Little Bighorn was fought in June, 1876, resulting in an overwhelming victory for the Lakota. The Lakota then spent the next several months skirmishing and dodging the Army. By May, 1877, with their people starving, Sitting Bull and Crazy Horse split. Sitting Bull fled to Canada leaving Crazy Horse to go to Fort Robinson to surrender. The Army spent the next 13 years restricting the movement and actions of the Lakota on reservations. In 1881, Sitting Bull returned to the US with the rest of the Lakota to surrender. Then the Army had little to no more trouble with the Lakota until the Ghost Dance scare of 1890. So, it was completely unrealistic to have a Lakota hunting party, turned war party, roaming the plains in 1883. The Army would not have allowed such a large hunting party (and accompanied by women and children) to leave the reservation. Perhaps parties of two or three could have sneaked off the reservation. But a hunting party this large (particularly with this many women and children) would have drawn the attention of the Army, which would have then sent a detail out after them to bring them back to the reservation.