Suspect Allegedly Unloaded His Entire Pistol in Texas Deputy Shannon Miles kept shooting downed officer, prosecutors say.

 -- A gunman unloaded his entire pistol into slain Harris County Sheriff's Deputy Darren Goforth when he stopped at a gas station near Houston Friday, prosecutors said in court today, adding that officials found 15 shell-casings at the scene.

Suspect Shannon Miles, 30, allegedly ran up to Goforth as he was filling up his tank and began firing immediately, Harris County District Attorney Devon Anderson said today at Miles' court appearance.

Anderson said Miles kept firing even when Goforth was on the ground.

"The gun holds 14 in its magazine and one in its chamber," Anderson said. "Fifteen shell casings; you can do the math. He unloaded the entire pistol into Deputy Goforth."

Goforth, 47, died at the gas station. Prosecutors said today Goforth was found face-down in a pool of blood.

An eyewitness, who saw the suspect flee, described the make and model of Miles' red Ford Ranger, prosecutors said, leading authorities to Miles' house. Prosecutors said they found a gun matching the ballistics of the gun that killed Goforth.

A witness viewed a video line-up and positively identified Miles as the shooter, prosecutors said.

Miles, who appeared disoriented in court today, remained cuffed throughout his appearance and wore yellow jail jumpsuit. He is facing a capital murder charge. No plea was entered. Miles was provided court-appointed attorneys Anthony Osso and Charles Brown.

The motive and origin of the gun have not been determined, Anderson said after court.

Anderson said she never expected to be at a crime scene Friday night, "looking at an officer dead on the ground."

"Houston is a very special place," Anderson said, where law enforcement is "treasured and valued."

The shooting appeared to be unprovoked, Harris County Sheriff Ron Hickman said Saturday.

"Our assumption is that he [the deputy] was a target because he wore a uniform," Hickman said Saturday. "At this moment, we found no other motive or indication that it was anything other than that."

Miles has a previous criminal history including resisting arrest and disorderly conduct with a firearm, according to Hickman.

Goforth, a 10-year veteran of the department, is survived by his wife, Kathleen, who works as a school teacher, and two children, ages 12 and 5, his brother-in-law Stephen Allison told ABC News.

"He was the rock in that family," Allison told ABC News through tears. "The kids loved him."

"I didn't have a brother... when they got together he was like the only other brother in my family," Allison said.

Kathleen Goforth said in a statement, "My husband was an incredibly intricate blend of toughness and gentility. He was loyal...fiercely so. And he was ethical; the right thing to do is what guided his internal compass.

"I admired his quality, perhaps, the most," her statement said. "For that made Darren good. And he was good. So, if people want to know what kind of man he was...This is it. He was who you wanted for a friend, a colleague, and a neighbor."