A California man who spent 33 years in prison for attempted murder has been declared innocent and freed, the Los Angeles County district attorney announced Thursday.

Daniel Saldana, 55, was convicted in 1990 of opening fire on a car containing six teenagers who were leaving a high school football game in Baldwin Park, east of Los Angeles. Two students were wounded but survived.

The attackers mistook the teens for gang members, authorities said.

Saldana was 22 at the time of the shooting and worked full-time as a construction worker. He was one of three men charged with the attack. Convicted of six counts of attempted murder and one count of shooting at an occupied vehicle, Saldana was sentenced to 45 years to life in state prison.

Saldana appeared with District Attorney George Gascón at a press conference announcing his exoneration Thursday. He said he was grateful to be freed.

“It’s a struggle, every day waking up knowing you’re innocent and here I am locked up in a cell, crying for help,” Saldana said, the Southern California News Group reports.

But, “I just knew that one day this was going to come,” Saldana said, according to CBS Los Angeles. “I’m so grateful. I just thank God.”

Gascón’s office began investigating after learning in February that another convicted attacker told authorities during a 2017 parole hearing that Saldana “was not involved in the shooting in any way and he was not present during the incident,” the DA said.

A former deputy district attorney was present at the hearing “but apparently did nothing” and failed to share the exonerating information with Saldana or his attorney as required, Gascón said.

That caused Saldana to spend an additional six years in prison before the DA’s office reopened the case and declared him innocent, Gascón said.

The district attorney didn’t disclose other details of the case but he apologized to Saldana and his family.

“I know that this won’t bring you back the decades you endured in prison,” he said. “But I hope our apology brings some small comfort to you as you begin your new life.”

Gascón added: “Not only is this a tragedy to force people into prison for a crime they did not commit, but every time that an injustice of this magnitude takes place, the real people responsible are still out there to commit other crimes.”

And though disappointed that the information took so long to reach his office, Gascón stressed the importance that justice was eventually served, CBS Los Angeles points out.

“As prosecutors, our duty is not simply to secure convictions but to seek justice,” he said in a statement. “When someone is wrongfully convicted, it is a failure of our justice system and it is our responsibility to right that wrong. We owe it to the individual who was wrongfully convicted and to the public that justice is served.”