Sept. 25, 2006  -- The shooting of a Houston police officer has sparked a new battle over immigration.

Juan Leonardo Quintero, an illegal immigrant, has been charged with killing a Houston police officer last week after a routine traffic stop.

Police Chief Harold Hurtt blamed the federal government for failing to secure U.S. borders.

Quintero allegedly shot Officer Rodney Johnson four times in the head while in handcuffs in the back seat of his patrol car.

Johnson arrested Quintero during a routine traffic stop for speeding but apparently missed the suspect's gun in a pat-down search.

Following the shooting, a video showed Houston police officers pulling open the back doors of Johnson's patrol car and yanking the suspect out of the back seat.

"It's very easy to make a mistake. I am not saying a mistake was made," one Houston police officer said. "Unfortunately, we are in the business where a mistake can kill you."

The suspect should not have been in the United States.

Quintero was deported in 2004 after a conviction for indecency with a child.

"The subject was deported, and yet he came back, so if the government fulfilled their responsibility of protecting the border we would probably not be standing here today," Hurtt said.

The Houston Police Department has been struggling this year to deal with the influx of Katrina evacuees and an immigration problem that is only getting worse.

Border Patrol said thousands of illegal immigrants crossed into the United States each month.

Johnson received a commendation for valor for pulling several children from a burning building.

He leaves behind a wife who is also a police officer and their five children.