(CNN) - The Las Vegas Metropolitan Police Department is investigating what happened during the arrest before the death of a man who repeatedly told officers that he couldn't breathe as he was being handcuffed.
The department's Force Investigation Team and Critical Incident Review Team are conducting investigations into the death of Byron Lee Williams, 50.
The findings will be forwarded to the Clark County District Attorney's Office for review, LVMPD Assistant Sheriff Charles Hank said at a press conference Tuesday. According to Hank, Williams' cause of death will be determined by the Clark County Coroner's Office.
Williams stopped for a traffic violation
Just before 6 a.m. on Thursday, LVMPD Officers Benjamin Vazquez and Patrick Campbell noticed Williams riding a bike in the pre-dawn darkness without a light, a traffic law violation, Hank said.
At a gas station, body camera video from one of the officers shows they flagged Williams down and yelled for him to stop, but he took off on the bicycle. As the officers followed him in their car, Williams ditched the bike and took off running.
Body cam video shows one of the officers chasing after Williams on foot and breathing heavily as he follows him over walls and into an apartment complex where the officer caught up with Williams and ordered him to get on the ground, which Williams did.
According to Hank, it was about a quarter of a mile chase.
In the body cam footage, the officers struggle with Williams to get him to put his arms behind his back.
In the video, Williams appears to keep his left hand in front of him.
Just before officers manage to get his hands in the handcuffs, Williams says, "I can't breathe."
He repeats himself. "I can't breathe, I can't breathe," Williams says.
An officer says Williams is out of breath from running.
"OK, I can't breathe, I can't breathe," Williams says in the footage.
In the footage, Williams is stood up and some items appear to fall from his body. Hank said the items later tested positive for methamphetamine and hydrocodone.
Police say a medical unit should be called
According to Hank, Williams' body went limp as officers tried to pull him off the ground, but he was still talking and trying to hide the fallen drugs with his feet. One officer joked on camera that Williams had "incarcer-itis."
On camera, someone asks if a medical unit should be called and officers say it should.
As they carried him to the patrol car, Hank said, Williams lost consciousness.
Las Vegas City Fire responded and treated Williams in the parking lot, Hank said, then transported him to a nearby hospital where he was pronounced dead at approximately 6:44 a.m.
"There was a time when the cameras went off after they got him over to the police car and they subsequently turned them back on later on," said Hank. But Hank said that department policy does allow for the officers to turn the camera off at the conclusion of an incident or in certain other circumstances.
Williams' niece wants to know what happened when the body cameras were turned off.
"We're missing a lot of footage," Teena Acree told CNN affiliate KLAS.
Hank said the officers involved will be interviewed to "evaluate if their camera was deactivated at the appropriate or inappropriate time."
"So it's premature for me to comment on whether or not those officers deactivated their cameras inappropriately, or if it was the activated appropriately," Hank said.
The entire incident from the chase to the arrival of the medical response was 14 minutes, Hank said.
'He was changing for the better'
Williams, who Hank said is a convicted felon with a long criminal history in California and Nevada, was part of the Clark County Detention Center electronic monitoring program, which required that he wear an ankle monitoring bracelet. But Hank said Williams had failed to check in in August and though he was wearing his ankle bracelet when he was taken into custody, he had not charged it, so other officers were seeking an arrest warrant for him when he was stopped for not having a light on his bike.
"He made bad choices, but guess what? He was changing for the better," Acree told KLAS. "Being arrested shouldn't turn into someone dying."
"We take the sanctity of life very seriously, and anytime -- something like this -- it's very unfortunate," Hank said.