(CNN) After 10 agonizing months hoping two officers would be charged for Alton Sterling's death, the Louisiana man's relatives didn't get the news they wanted.

Federal prosecutors announced Wednesday that there isn't enough evidence to warrant civil rights charges against Baton Rouge police officers Blane Salamoni and Howie Lake II.

But they said they would hand the case files over to Louisiana Attorney General Jeff Landry, who will determine whether state charges are appropriate.

Sterling, 37, was killed by police in July 2016. Cellphone video showed Sterling, a black man, pinned to the ground by the white officers before he was shot, but police said he was reaching for a gun.

Outrage over Sterling's death led to renewed "Black Lives Matter" protests across the nation.

Landry said state police will lead Louisiana's investigation, and a prosecutor from the state's Department of Justice will assist.

"A thorough and complete investigation could take a considerable amount of time; as such, we ask for patience from the public and the press," Landry said.

The US Department of Justice's decision was disappointing to the Sterling family, attorney Chris Stewart said. But "we're not angry. We're not gonna ... let rage rule, because it's not over," he said.

Officer pointed gun at Sterling's head

Alton Sterling

There were some revelations in the Justice Department's announcement. One new detail: The officer who eventually shot Sterling first put a gun to his head when Sterling didn't comply with orders to put his hands on the hood of a car on the night of July 5.

Video shows the officers put their hands on Sterling after he refused their order and struggled with them.

Salamoni then pulled his gun.

Stewart said they learned in a conversation with federal prosecutors and investigators that Salamoni also said, "I'll kill you, bitch."

Authorities, citing the ongoing investigation, would not comment any further on the case.

After the news conference, Alton Sterling's aunt's emotions burst out, according to CNN affiliates WAFB and WBRZ

"Oh my God, that was the hardest thing ever," Sandra Sterling wailed, before her attorney and others led her away from reporters. "To hear Salamoni tell my nephew, my child who I love so much, that I'm going to kill you. He put that gun to his head. ... Salamoni put that gun to his head and said I'm going to kill you. So how do you think Alton felt? How do you think Alton felt after hearing that I'm going to kill you?"

Stewart said Salamoni instigated the situation.

"The most important thing is it shows the mindset of Officer Salamoni," he told CNN.

Salamoni's attorney, John McLindon, told CNN he doesn't know whether his client said those words.

"I was not a part of that conversation the Sterling family had," he said Wednesday evening. "The US attorney did allude to the officer's behavior not being appropriate."

"If it did happen, then the feds knew about it," McLindon said. "If it's on video or audio, they have it. And they used two separate expert witnesses on use of force. Both of them reached the same conclusion -- that it was not criminal behavior. If it did happen, it did not rise to the level of criminal conduct."

The DOJ announcement also says that after the officer -- responding to a 911 call about a man with a gun -- confronted Sterling with his service pistol, the suspect put his hands on the car hood. When Sterling took his hands off the hood, Lake tasered him and both officers tackled Sterling and took him to the ground.

Among the other things we learned Wednesday:

• The Justice Department identified Sterling's gun as a .38 caliber revolver, with six rounds in it.

• While two videos showing the incident have been released publicly, there are four other videos in evidence: two body camera recordings, one from a store surveillance camera, and one from the dashboard camera in a patrol car.

• Lake twice used his Taser on Sterling before the scuffle.

Justice department: Not enough evidence for federal charges

Federal prosecutors concluded there is not enough evidence to support civil rights charges against either officer.

JUST WATCHED Alton Sterling's son speaks out Replay More Videos ... MUST WATCH Alton Sterling's son speaks out 02:08

"We would have to prove, beyond a reasonable doubt, that Officer Salamoni did not believe that Mr. Sterling was actually going for a gun ... and that he simply decided to shoot him," said Corey Amundson, acting US attorney for the Middle District of Louisiana.

Several of Sterling's relatives wept after the DOJ told the family no federal charges will be filed. But Stewart said he thinks the state will find reason to charge the officers.

Lake's attorney, Fred T. Crifasi, called the shooting a tragic loss.

"It has drastically changed the lives of all those personally connected and has indirectly affected so many more. While Officer Lake is certainly relieved by the conclusion reached by the United States Department of Justice, he is aware that this investigation is now in the hands of the Attorney General for the State of Louisiana," he said. Accordingly, he will continue to refrain from publicly commenting on the facts of the case."

McLindon said he agreed with the Justice Department's decision "100%" and will contact the Louisiana attorney general on Thursday about cooperating with the next investigation.

The mayor of Baton Rogue said the fatal shooting will lead to revisions in the city's police training manual about the use of force.

Mayor Sharon Weston Broome also said $2 million would be put toward toward securing body cameras for the entire force. Officers will also receive training in implicit bias, she told reporters.

Shot on the ground

The killing gripped the nation because two bystander videos , each less than a minute long, captured Sterling's struggle with the two officers.

JUST WATCHED Witness: Sterling's gun was not visible at any point Replay More Videos ... MUST WATCH Witness: Sterling's gun was not visible at any point 01:59

Sterling's fatal encounter with police started when he was standing outside the convenience store where he frequently sold CDs and DVDs. Someone called 911 to report a man outside the store with a gun.

Bystander video -- which apparently begins after Salamoni pointing his gun -- shows an officer rushing Sterling and pulling him to the ground. The other officer helps restrain Sterling. Someone shouts, "He's got a gun!"

Police eventually manage to pin Sterling to the ground, with one officer straddling him. In one video, an officer draws something from his waistband and points it at Sterling. As the camera turns away, more yelling ensues, followed by several loud bangs.

Afterward, the camera captures Sterling with a large bloodstain on his chest as an officer on the ground next to him keeps his gun pointed at Sterling.

As Sterling lies fatally wounded, the other officer removes something from Sterling's right pocket.