This undated photo from a surveillance video provided by the Houston Police Department shows a man that Houston police are labelling a person of interest in their investigation of the slaying of Josue Flores as he walked home from school May 17, 2016. Police Sgt. Tommy Ruland says detectives are looking for the public's help in identifying the man as they try to solve the stabbing death. (Houston Police Department via AP)

HOUSTON - A 27-year-old ex-Marine from Houston has been charged with murder in the stabbing death of an 11-year-old who was walking home from school last month, police said Saturday.

Andre Timothy Jackson Jr. was arrested Friday afternoon at the Salvation Army in downtown Houston and charged later in the day, Mayor Sylvester Turner said at a news conference Saturday. Jackson is being held in the Harris County Jail on $100,000 bond. It wasn't immediately clear whether he had an attorney.

Jackson, who police said was discharged from the Marines in 2011, is accused of stabbing Josue Flores as the sixth-grader walked home from school May 17. Josue was only a few blocks from home.

"We cannot bring him back, but I hope today's announcement can perhaps bring a little bit of comfort to those who love him," Turner said. "Our minds search for answers that just aren't there. What we do know is it was senseless, it was brutal, it was cold-blooded. And someone needs to pay the price for it and justice needs to be rendered."

There is no motive in the slaying and no known connection between Jackson and Josue, Lt. John McGalin said Saturday.

Jackson is a veteran who had lived at the Salvation Army since mid-April, McGalin said. It wasn't immediately clear which branch of service Jackson served in.

Earlier this week, authorities released surveillance video featuring a "person of interest." The 36-second video showed a man running down a street not far from the scene wearing a green jacket with a partially obscured word containing the letters "LYMEN" on the hood of the jacket.

The video brought a tip about another video, which led investigators to Jackson, McGalin said. Jackson had the jacket with him when he was arrested, McGalin added.

Authorities initially charged a 31-year-old man with a long criminal history days after the killing, but that charge was dropped when detectives found evidence to support his alibi.

Questioned Saturday about how he was sure the right man has been arrested, McGalin said that Jackson's alibi could not be verified and that he "provided a statement that corroborated a lot of things we knew to be true and led us to believe we have the right guy."

Several witnesses told officers they heard loud screaming and saw Josue struggling with a man. The boy collapsed on the grass near the sidewalk and the man ran off. A bystander flagged down police and alerted them to the wounded boy, who was taken to a hospital with multiple stab wounds and pronounced dead a short time later.

Investigators reconstructed the suspect's trail using video from residents' homes and businesses, McGalin said, though some of the surveillance footage came in slowly.

"People didn't know what they had until we went and knocked on their door and actually caught them at home," McGalin said. "We pieced it together. We believe we know the track that the suspect walked."

Authorities will determine how a reward for information in the case that had grown to $45,000 will be disbursed, McGalin said.

News from © The Associated Press, 2016