If the DA wanted the guy to be indicted, he would have been indicted. That's how grand jurys work and grand jurys are not courts as evidence is presented from only one side. The DA, being an elected official, knew that to indict the guy would cost her her job. Her actions were political.
What if the rapist were not a 47 year old male but a 13 year old male? What is the rapist were a woman? Would the instant death sentence still have been appropriate?
No prosecuting the guy when his actions were clearly justified by Texas statue would have been political.
Deadly Force in Defense of Person
"A person is justified in using deadly force against another if he would be justified in using force under Section 9.31 of the statute when and to the degree he reasonable believes that deadly force is immediately necessary to protect himself against the other's use or attempted use of unlawful deadly force, if a reasonable person in the same situation would have not retreated. The use of deadly force is also justified to prevent the other's imminent commission of aggravated kidnapping, murder, rape or robbery."http://www.self-defender.net/law3.htm
Other than 47 yo males are less loveable than youngsters or women I'm not sure what that has to do with the price of tea in China. If they were attacking/raping a 5 yo child and the father or whoever uses deadly force to stop them, too bad so sad, what the hell did they think could happen.