A motive remains elusive as investigators in Texas try to determine why a 30-year-old suspect in custody would have gunned down a sheriff's deputy while he was fueling his patrol car at a gas station near Houston.

Shannon J. Miles, 30, was charged Saturday in what authorities have described as an "execution-style" killing of 47-year-old Harris County Sheriff's Deputy Darren Goforth.

The Associated Press reports that Goforth had "gone to the station in Cypress, a middle-class to upper middle-class suburban area of Harris County that is unincorporated and located northwest of Houston, after responding to a routine car accident earlier Friday."

In a news conference announcing the arrest on Saturday, Sheriff Ron Hickman said the attack was "clearly unprovoked," and that there is no evidence so far that Goforth knew Miles.

"Our assumption is that he was a target because he wore a uniform," Hickman said.

The Houston Chronicle reports:

"Goforth had been with the sheriff's office for 10 years. He was stationed in District V in northwest Harris County. He had a wife and two children, a 12-year-old daughter and a 5-year-old son."Friends and colleagues described him as a compassionate and hardworking deputy."The shooting shocked neighbors of the suspect, plunged Goforth's family and friends into grieving and left law enforcement officials pointing to heightened tensions between police and the public, sparked by recent high-profile violent incidents, as a possible motive."

Hundreds of people attended a vigil on Saturday night to remember the fallen officer, Reuters reports.

"I wanted to demonstrate that all lives matter, regardless of color," Carol Hayes, an African-American woman, told a local NBC News affiliate.

Deray McKesson, a leader of the Black Lives Matter movement, was quoted by the Chronicle as saying: "I grieve for the victims of violence. It is unfortunate that Sheriff Hickman has chosen to politicize this tragedy and to attribute the officer's death to a movement that seeks to end violence."

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