Citing DNA testing, Houston officials have dropped a murder charge against the man they accused of killing 11-year-old Josue Flores last year

Citing DNA testing, Houston officials have dropped a murder charge against the man they accused of killing an 11-year-old boy last year, PEOPLE confirms.

The Harris County District Attorney’s office says there is “insufficient evidence to prove a case against” Andre Jackson, a 28-year-old former Marine who has spent the last year behind bars in connection with the May 17, 2016, death of Josue Flores.

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Jackson was freed Tuesday after the charge against him was formally dropped.

Prosecutors said testing of DNA evidence returned “inconclusive” results that “in some ways exclude” Jackson as a suspect — but noted that authorities reserved the right to refile murder charges in the event new evidence is unearthed.

According to the Houston Chronicle, the DNA on Jackson’s clothes did not match Josue and the DNA on Josue’s clothes did not match Jackson.

Jackson, who was reportedly homeless at the time of the death, was accused of killing Josue as the boy was making his way home from school last May. The middle school student was stabbed more than 20 times, according to officials.

Jackson was arrested in early June 2016 and allegedly confessed his involvement in the child’s vicious slaying.

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Image zoom Andre Jackson Houston Police Department

No other suspects have been named and prosecutors stressed that Jackson has not been exonerated, even in light of the DNA test results. Still, they have issued a new call for tips from the public.

A statement from the Houston Police Department reaffirms “our homicide detectives believed then and continue to believe that Mr. Jackson is the suspect in this case.”

“We’re not saying Andre Jackson is innocent and excluded as a suspect,” prosecutor Tiffany Dupree told the Chronicle. “We’re just saying at this point, if we tried this case to a jury, we don’t feel we could secure a conviction.”

Jackson’s attorney could not be reached for comment. But speaking to the Chronicle, he said, “Since about November of last year, my office and myself were convinced that Mr. Jackson could not have committed this offense. We were waiting for those results from the DNA, and frankly, I was not surprised.”

“His family is very eager to have him back home and they do not live here in Houston,” Jackson’s attorney told the paper.

Flores’ family was unavailable for comment, but in a statement to local TV station KTRK, the boy’s sister Guadalupe Flores said they were “too devastated and broken up” about the new developments.

She said that she could not believe “that a killer is being let loose due to insufficient evidence.”

“I know it doesn’t matter what I think, but in my heart I know that he is the killer,” she said. “But I know there’s not enough evidence for them to keep him in jail, but that’s how the system goes. If they don’t have any evidence, they have to let you go.”

Jackson is the second suspect whose charges were dropped after being accused as Josue’s killer. Another man, Che Calhoun, was arrested only days after Josue died but was quickly cleared.