A new video has emerged allegedly showing a US officer fatally shoots a suspect who appears to be lying handcuffed and motionless on the ground.

The cellphone video has prompted the prosecutors of the Salt Lake City, Utah to reopen their investigation into the death of James Barker, 42, by officer Matthew Taylor on January 8, 2015.

Taylor, who was responding to reports of a man knocking on doors in the Salt Lake City neighborhood, confronted Barker, who, according to his partner, had gone to shovel ice.

Taylor's body-mounted camera showed the officer approaching the suspect on a patio. A confrontation ensued in which Barker yelled, "I'm trying to make a living," and then swung his shovel at the officer.

However, the camera was knocked off of Taylor and cut out about 20 seconds later. The new video, taken by a Barker's neighbor, shows Taylor standing over Barker, as he is lying on the ground and a series of sounds can be heard.

Former Davis County Sheriff William Lawrence and others believe the sounds heard at the beginning of the enhanced video to be gunshots.

"From my experience, the thousands of times that I've heard gunshots, it sounds to me very clearly to be gunshots," Lawrence, who released the video publicly, told NBC affiliate KSL. "I need answers, this disturbs me."

In February, 2015, Taylor was exonerated of any wrongdoing by Salt Lake County District Attorney Sim Gill.

However, Gill himself released the new footage on Friday, announcing plans to take a second look at the incident.

“Our job and our commitment has always been [to be] as thorough and open and transparent as we can,” Gill told the Tribune. “So we are going to do our due diligence to re-examine what we have.”

The Salt Lake City District Attorney's Office is going to ask experts to authenticate the footage and help determine whether the sounds are actually gunshots.