HOUSTON -- Immigration officials admitted on Thursday that an "old system" of tracking illegal immigrants who commit crimes allowed one suspect to remain in the United States for nearly two decades before Tuesday's fatal shooting of a Houston police officer, KPRC Local 2 reported.

Senior HPD Officer Henry Canales, 42, was killed Tuesday at about 9 p.m. during an undercover sting aimed at groups that buy stolen merchandise.

The man who police said killed him was shot and killed by Canales and another officer.

Two adults and a teenage girl are jailed on capital murder charges, accused of taking part in the robbery that ended in Canales' killing.

Harris County District Attorney Pat Lycos told an afternoon news briefing that it is premature for her to decide whether to seek death on the two adults.

HPD Homicide Squad Capt. Steve Jett said the gunman was shot by the officer once through the chest in what could have been a fatal wound. Then, after the officer collapsed, the second officer struggled to detain the shooter, and then shot him through the back as he raised the gun back over his shoulder.

Jett stressed that the second officer didn't even realize the gunman was still armed as he struggled, but then shot the gunman in the back as he turned the gun toward the officer behind him.

HPD leaders and Lycos emphasized that the undercover operation was aimed at keeping the streets safe, only targeting large groups of people organized for buying stolen goods. HPD said the group in this week's fatal shootout brought the money and was ready to buy a truckload of stolen televisions.

Lycos said that if there is no market for stolen goods, "we're all safer."

Jett said surveillance of the undercover TV buy showed only 42 seconds between the time police were negotiating the deal and the gunman turning to rob the officers of the TVs, the truck, and their money. Jett said the officer never had time to identify himself as an officer.

Immigration and Customs Enforcement leaders told the afternoon briefing that it has identified nearly 14,000 illegal immigrants subject to deportation in Houston this year through the 287(b) program. That is the search of jails and other databases that the city just started taking part in after an illegal immigrant shot and wounded narcotics squad officer Rick Salter in March.

ICE officials said their old computer system prevented them from throwing one career criminal out of the country after many arrests over the past two decades.

Andres Nava-Maldonado had eight aliases, according to HPD and several arrests dating back to 1990 in California.

He is one of the people arrested leaving the scene.

HPD said Maldonado was never in trouble here, but in California he was arrested for attempted murder in 1990, a charge that was reduced down for some reason. He was charged in June 1990 with being under the influence of drugs, and then October 1990 for robbery, a charge that was dismissed for lack of probable cause.

He was charged in February 1991 with assault and given 30 months probation, in November 1990 charged with false identity given to police officer, for which he served 10 days in jail and three years probation. Hour was charged in October 1991 with grand theft and assault and then in 1992 charged with exhibiting firearm.

Despite all those arrests, ICE leaders maintained he was not deported because their old system did not catch it. Agent-in-charge Robert Rutt said a new system now in place would catch such a thing.

The second adult suspect, illegal immigrant Xiomara Mendez-Rosales, 36, had two prior arrests from HPD in 2006 for domestic violence assault. Both of those cases were dismissed.

Jett said a deportation order had been placed against her then, but HPD would have no way of knowing about that because only criminal cases come up on suspect name searches.

Deportation is a civil process, he said, so HPD had no idea she was supposed to be deported when officers originally arrested her.

The dead gunman, Roberto Pedroza Carillo, 37, had three aliases, but HPD said no arrests were found on his record.

Houston Police Chief Harold Hurrt told KPRC Local 2 he is not planning any changes to undercover protocols or proactive stings based on this shooting.