Dozens of lives were spared in the hostage situation in Colorado Springs Tuesday, partly because of one courageous surgeon. He tells 11 News he was ready to do whatever it took to make sure everyone got out.

Doctor Jeff Ferguson didn't want it known that he's licensed to carry a concealed weapon, but Tuesday- he didn't have a choice. On the phone he told 11 News, from the sound of the gunman's voice, he felt like someone was going to get hurt.

"This (gunman), when you heard his voice, I was expecting any second to hear the shots ring out. I thought ok, this guy's going to start shooting people right now," Dr. Ferguson said.

Dr. Ferguson's inside story of what happened inside the building, 75 Printers Parkway. He says Dominic Oliver was yelling as he pulled out his gun in the reception area.

"(Oliver) said, ‘Everyone get on the ground’ and it was chaos after that as you can imagine," Dr. Ferguson said.

In the chaos, employees started shouting about another exit way, one Dr. Ferguson didn't want the gunman to know about. He guarded the exit with his gun, allowing everyone else to escape and ready to shoot if he had to.

"If this guy opens this door, I’m going to have to shoot him,” Dr. Ferguson said. “You were prepared to do that? I was absolutely prepared to shoot him, yes."

Dr. Ferguson got out and gave SWAT valuable information about the layout and the man inside.

"I said (to CSPD officers) you can't see over the top of the stairway, it's a narrow, very steep stairway. It's basically an ambush because I don’t know where he is," Dr. Ferguson said.

Oliver man was the only one injured, and that's remarkable. 11 News was the only crew there as medics rushed him out of the ambulance and into the E.R., where later he died.

Dr. Furgeson said he's most impressed by the response time of CSPD and their tactical units, making sure no one else was hurt.