Close combat class firearm instructor unintentionally shoots instructor during training class

Former Russian soldier and current firearms trainer and video host Sonny Puzikas was teaching a "close combat class" at the Texas Defensive Shooting Academy in Ferris, Texas.
According to the founder of the academy, the range "allows shooters the ability to shoot the way they want, without the stringent rules imposed like most other ranges."
The class was being held in a section of the range called "the city", a live fire area with multiple rooms and targets. This particular class had a three room shoot house, each room with multiple targets. Students were taken through the house one at a time and used live ammunition to shoot at the targets.
The last students were going through the shoot house and it was getting dark. According to Sonny:

"I knew the last shooter was going inside to shoot. I heard the shooting shop. I did not hear shooting for a while. I finished saying good-bye so I decided to make a run in the house before I left. I made the statement, 'I am going to do a run' and then I heard a person standing behind me respond to me saying, 'OK' I did not turn around so I don't know who said OK to me. I, wrongfully, assumed it was clear to go. I pulled my pistol out and set up and started coming around the corner. I shot three quick shots at the far left target, then three quick shots at the far right target and then three quick shots at the close right target just insdie the room. I then heard someone say, 'You shot me.'

Sonny had unintentionally shot his assistant instructor, Gene Smithson. Smithson was shot three times, twice in the abdomen and once in the right bicep and hand. He was taken to the local hospital and is expected to survive.