"The message we're trying to send today is the criminal justice system works," Harris County District Attorney Kenneth Magidson said.
Horn's attorney, Tom Lambright, has said his client believed the two men had broken into his neighbor's home and that he shot them only when they came into his yard and threatened him.
Horn's attorney, Tom Lambright, said his client was relieved by the grand jury's decision and never wanted to hurt anyone.
"He wasn't trying to take matters into his own hands," Lambright said. "He was scared. He was not playing cowboy."
Horn did not speak with reporters Monday, and had a "No Trespass" sign blocking the path to the front door of his home.
Lambright said Horn believed the two men had broken into his neighbor's home and that he shot them out of fear for his life when they came into his yard and threatened him.
"He wasn't acting like a vigilante," Lambright said. "He was well within his rights to do what he was doing."
The men Horn killed, Hernando Riascos Torres, 38, and Diego Ortiz, 30, were unemployed illegal immigrants from Colombia. Torres was deported to Colombia in 1999 after a 1994 cocaine-related conviction.
The episode touched off protests from civil rights activists who said the shooting was racially motivated and that Horn took the law into his own hands. Horn's supporters defended his actions, saying he was protecting himself and being a good neighbor to a homeowner who was out of town.
"I understand the concerns of some in the community regarding Mr. Horn's conduct," Magidson said. "The use of deadly force is carefully limited in Texas law to certain circumstances ... In this case, however, the grand jury concluded that Mr. Horn's use of deadly force did not rise to a criminal offense."
Lambright did not immediately return a phone call seeking comment from The Associated Press.
Texas law allows people to use deadly force to protect themselves if it is reasonable to believe they are in mortal danger. In limited circumstances, people also can use deadly force to protect a neighbor's property; for example, if a homeowner asks a neighbor to watch over his property while he's out of town.
It's not clear whether the neighbor whose home was burglarized asked Horn to watch over his house.
Statement from City of Pasadena
With a decision by the grand jury not to return a true bill against Mr. Horn, a panel of citizens drawn from the community has determined that the facts of the incident did not warrant the handing up of an indictment for criminal actions. The grand jury, hearing the available facts and witnesses as well as the law to be applied in this case, is in the best position to make that determination.
Mr. Horn has satisfied the state, through the grand jury process, that his actions do not warrant criminal prosecution on these charges. We hope that the decision of the grand jury, while difficult for some to accept, will be respected as the product of a careful weighing of all the facts by an impartial panel of citizens.
This incident has been a tragedy for all those involved, changing lives forever. The obvious lessons that can be drawn from it are that criminal activities are inherently a dangerous lifestyle, and the prevention and pursuit of those involved in criminal actions are best left to the police. They are professionals trained to meet the unexpected circumstances of pursuit and apprehension. The City of Pasadena intends to continue to provide its police force whatever resources required to assure our citizens that their community remains a safe place to live and work.