Dog the Bounty Hunter's Cop Son Reinstated After Fatal Car Crash

9:32 AM PST -- Garry Chapman's attorney Scott Morro tells TMZ… his client was reinstated, but first must complete a 120 hour suspension from the Priceville Police Department. He says they disagree with the decision and plan to appeal, plus file a lawsuit.

Dog the Bounty Hunter's son is back in the police force in Alabama after being placed on leave -- and then fired -- following his involvement in a fatal high-speed car chase, TMZ can confirm.

Dog -- real name Duane Chapman -- posted the exciting news on social media Tuesday evening, sharing himself and several smiling family members surrounding his son Garry Chapman, who was dressed in a gray suit.

He celebrated the victory in a lengthy caption and praised his son for acting "with honor, courage, and integrity while doing his job to protect and serve" from the start, while also denouncing the car chase suspect.

Priceville Police Department Police Chief Jerry Holmes confirms to TMZ the decision was made Monday night, with the city council voting to repeal his firing. They instead gave him a 10-day suspension without pay.

He tells TMZ it's unclear why the council overturned Garry's firing ... but says he does not believe it had to do with involvement from Dog. He says he never spoke to the reality star, and he had "nothing to do with this process."

He adds ... "It is the process in place if an employee appeals the termination, they first appeal to the Mayor. If the Mayor does not overturn it, then the employee has to request for a hearing before the council which is what happened in this case."

TMZ has reached out to Priceville Mayor Sam Heflin for comment ... so far, no word back.

As we reported ... Garry was behind the wheel of a Sept. 6 chase that left 6 people hospitalized and 17-year-old Tristan Hollis dead.

He was swiftly placed on leave by the Priceville Police Department and then fired several weeks later.