The sheriff’s deputy who was killed “execution style” at a suburban Houston gas station was shot 15 times at close range and left to die “face-down in a pool of his own blood,” a prosecutor said in court Monday.

Shannon J. Miles. (Harris County Sheriff’s Office)

Shannon J. Miles, 30, appeared in a yellow jumpsuit in Harris County’s 208th criminal court, where he was arraigned on a capital murder charge. Harris County District Attorney Devon Anderson accused Miles of firing 15 rounds into deputy Darren Goforth’s back and head at a Chevron station in Cypress, Tex., on Friday night, in what police have called “an unprovoked, execution-style killing of a police officer.”

“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.”

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Goforth had just filled up his patrol car and walked inside the gas station when a witness saw a man sitting in a red Ford Ranger pickup truck parked outside, Anderson told the judge, according to KPRC-TV. Surveillance video showed the man jump from the truck and run up behind Goforth as he exited the store, holding a handgun to the back of his head and pulling the trigger. Goforth fell to the ground and the man continued to pump bullets into his back, she said.

Goforth, 47, was a 10-year veteran of the Harris County Sheriff’s Office. No motive was discussed in court, but according to the Associated Press, Harris County Sheriff Ron Hickman has said that “our assumption is that [Goforth] was a target because he wore a uniform.”

Miles was arraigned shortly after Gov. Greg Abbott (R) ordered all Texas flags in Harris County and at the Capitol in Austin to be lowered to half-staff to honor Goforth. In a statement, Abbott said the state had seen a “deliberate and heinous crime” against a law enforcement officer, according to the Associated Press.

Goforth’s funeral has been set for 11 a.m. Friday at Second Baptist Church in Houston, according to the Harris County Sheriff’s Office.

Investigators traced the truck to a Houston-area home and saw a vehicle matching its description parked in the driveway. A man at the house told police it belonged to his brother, who was not at home. When Miles returned, he told police the truck was his, Anderson said.

Miles also told police he owned a handgun, which he said was stored in his garage. Police obtained a search warrant, searched the home and found the weapon, which was empty. But ballistics tests showed it matched the bullets found at the crime scene, Anderson said.

Deputy Darren Goforth (Harris County Sheriff’s Office)

Still, Miles’s mother, who has asked not to be named, told reporters that her son could not have committed the crime. Over the weekend, she told NBC News that her son was shopping with her at the time of the shooting; she told KPRC-TV that he was at home when it happened. “My son ain’t killed no cop,” she told the station.

According to ABC News, Miles “appeared disoriented in court” on Monday.

No plea was entered. Miles was provided court-appointed attorneys Anthony Osso and Charles Brown.

In a few weeks, the case will go to a Harris County grand jury, which is expected to indict Miles. If convicted, he could face the death penalty.

“The shooter in this case didn’t see black, he didn’t see white; he saw blue,” KPRC-TV legal analyst Brian Wice said. “That’s what this case is about. In another year, the DA’s office is going to ask 12 Harris County citizens to probably ask this defendant to pay with his life for this execution.”

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Miles has had multiple misdemeanor convictions over the years. In 2005, he was found guilty of criminal mischief, giving false information to police and resisting arrest, according to court records cited by the Associated Press. The next year, he was convicted of disorderly conduct with a firearm. In 2007 and 2009, he was convicted for evading and resisting arrest.

He has had several short stints behind bars.

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The most recent — and serious — charge comes amid nationwide protests over perceived police brutality, particularly against African Americans. Following the police-involved killings of Michael Brown and Eric Garner, “Black Lives Matter” has turned from a phrase into a global movement. Goforth, the slain deputy, was white. Miles, the suspected gunman, is black.

“We’ve heard ‘black lives matter.’ All lives matter. Well, cops’ lives matter, too,” said Hickman, the sheriff. “So why don’t we just drop the qualifier and just say ‘lives matter,’ and take that to the bank.”

Two police officers in East Texas gained national attention this month while trying to make that statement. The men — one black and one white — posted a photo online showing a message “His life matters” inked on their hands with arrows pointing to each other. Other officers have posted similar photos, provoking a larger discussion about senseless violence.

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Following Friday’s shooting, the gas pump near where Goforth was killed became a makeshift memorial packed with flower bouquets, balloons and American flags to honor the fallen officer. Hundreds of supporters joined law enforcement Saturday, collecting more than $15,000 for Goforth’s family, according to the Houston Chronicle. More than 1,000 people attended a vigil there Sunday night.

“I couldn’t do nothing,” Christine Bossi, who led a roadside collection effort, told the newspaper. “We need to be a community. We need to stick together. We need to be here with our officers fighting for them just as much as they fight for us.”

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Over the weekend, people on social media started sharing photos and videos showing their support with the hashtag #DeputyDarrenGoforth.

This post has been updated.