A 30-year-old Houston man facing a charge of capital murder in the killing of a deputy was arraigned on Monday in a case the county sheriff tied to the "Black Lives Matter" campaign against police violence.

Shannon Miles did not enter a plea at the court proceeding, where Harris County District Attorney Devon Anderson detailed the case against him.

Miles, who is being held without bond, is accused of fatally shooting Deputy Darren Goforth in the back on Friday evening at a Houston-area gas station as Goforth fueled his patrol car.

Deputies found Goforth face down in a pool of blood near his patrol car, dead from multiple gunshot wounds, Anderson said in court. Fifteen 40-caliber shell casings were around him, she said.

Surveillance video showed a black male shooting Goforth, a 10-year veteran officer, in the back of the head and standing over Goforth and shooting more, Anderson said.

Deputies searched Miles's garage and found a loaded 40-caliber gun and the same brand of ammunition as the casings found at the scene, Anderson said. Forensic testing determined the gun was the one fired at the scene, she said.

"He unloaded the entire weapon into Deputy Goforth," Anderson said.

A witness positively identified Miles in a lineup as the shooter, Anderson said.

Texas Governor Greg Abbott on Monday ordered state flags in Harris County to be lowered to half-staff in honor of Goforth.

NBC News reported that Miles's mother said her son could not be the gunman because he was shopping with her at the time.

Harris County Sheriff Ron Hickman has linked the shooting to anti-police rhetoric following protests against deaths of unarmed black men at the hands of white officers around the country. Goforth was white and the suspect is black.

Hickman said the department assumed Goforth was a target because he wore a uniform.

"We've heard black lives matter; all lives matter. Well cops' lives matter too," Hickman said. "At any point where the rhetoric ramps up to the point where calculated cold-blooded assassination of police officers happen(s), this rhetoric has gotten out of control."

During the past decade, Miles has been convicted of several crimes including resisting arrest, disorderly conduct and trespassing, court records showed.

More than 1,000 people attended a prayer vigil on Saturday and a prayer walk on Sunday for Goforth and in support of law enforcement, Anderson told reporters after the court hearing.