FYI, Johnson has NOT been formally charged with a crime -- and ADAMANTLY DENIES THE ALLEGATIONS -- but officials are clearly laying out their case against the running back ... and it's compelling stuff.

Long story short, officials believe CJ2K rewarded a gang member with cash after the guy allegedly killed two men who were suspected of gunning down Johnson's friend in 2015.

Here's the backstory ... Johnson nearly died in a shooting in Orlando, Fla., back on March 8, 2015 ... when Orange County Sheriff officials say someone opened fire on a Jeep that Chris was in at around 4 AM.

Johnson suffered a bullet wound to his shoulder and made a full recovery ... but the driver of the vehicle, his friend, Dreekius Johnson, did not survive the attack.

In new court docs ... law enforcement officials say "intelligence gathered suggested [the shooting] was a gang related murder attempt on Chris Johnson."

Officials also say ... months later, a noted Florida gang member named Dominic Bolden shot and killed two men -- one on Jan. 19, 2016 and one on July 24, 2016 -- who were believed to be the shooters in the March 2015 incident.

In the court docs, officials claim an informant told them as a reward for Bolden's alleged actions ... Chris helped the guy become a leader of a famed drug trafficking organization (DTO) in Florida.

The informant told officials that Johnson supplied Bolden "with funds and an individual who could continually supply Dominic Bolden with as much narcotics as needed to supply the DTO."

The informant also told officials the "murder for hire elevated Dominic Bolden's rank, reputation and power within the DTO" -- eventually making Bolden the org's de facto leader.

At the time of the March 2015 shooting, Chris was tagged in a social media post that appeared to be a threat directed at the gunmen ... but Chris denied he was seeking revenge, saying, "I don't live that life."

In the docs, 34-year-old Johnson is also accused of helping with day-to-day operations of the DTO ... but court records show he has NOT been formally charged with any crimes.

We've reached out to prosecutors at both the state attorney's office and the attorney general's office in Florida for comment on the investigation ... but so far, no word back yet.

We also reached out to Chris -- and a rep for the former NFL star tells us he strongly denies the allegations ... saying, "There's no validity to any of these accusations."

Chris is considered one the NFL's most exciting players EVER -- recording 9,561 rushing yards in his 10-year career.