(CNN) Graphic video shows the minutes leading up to the death of a Virginia man while in police custody.

Officers can be seen tasing Linwood Lambert, 46, multiple times while he is handcuffed, outside a hospital where the officers had initially taken him for medical help.

The incident happened in May 2013 in South Boston, a town of 8,000 in southern Virginia, but it is receiving renewed attention after a report aired Wednesday on MSNBC

According to a medical examiner's report, Lambert died after going into cardiac arrest. The cause of death was listed as "acute cocaine intoxication" and the manner of death as an accident. Lambert's family disagrees and has reportedly filed a civil suit against South Boston police alleging excessive force, wrongful death and denial of medical care. They are seeking $25 million in damages.

Family attorney Joe Messa said he couldn't believe what he was seeing on the video.

"It's outrageous. It's uncalled for," he said. "It's the kind of thing that shocks your conscience, and it shocks my conscience as an attorney and should shock the conscience of the public."

Police have denied the allegations. They say Lambert's erratic behavior required the use of force.

"We are vigorously defending the case on behalf of the South Boston Police Department and its officers as we strongly believe the defendants did nothing wrong in their interaction with the late Mr. Lambert on May 4, 2013, and that their actions did not cause his death," read an attorney statement. "Our position is affirmed by the reports of two independent, well qualified experts in the field."

CNN attempted to contact the South Boston Police Department but has not heard back.

The Virginia State Police completed its investigation in October 2013, according to a spokesman, and handed the case over to Halifax County Commonwealth's Attorney Tracy Quackenbush Martin. She's still reviewing the case.

"This is an extremely serious matter. It's one that requires extraordinary deliberation and it's imperative to me that I reach the correct decision -- not only the correct decision but in the correct way and in a way that inspires public confidence to the extent that that is possible," Martin said.

"I am doing everything that needs to be done for this case. I'm leaving no stone left unturned, and it's my hope that people and the press will see that when it's over," she said.

The video begins with officers picking Lambert up at a motel after receiving a call about a disorderly subject.

He was not armed and not accused of any crime.

But officers say they decided to take Lambert to the hospital for a mental health evaluation anyway, after he made some disturbing comments.

Inside the patrol car, police say Lambert kicked a window. Video shows him bolting out of the car and running toward the doors of the hospital while handcuffed.

Lambert doesn't make it inside. The officers give chase and appear to tase him multiple times. He falls to the ground. They tell him to get on his belly and threaten to tase him again if he does not comply.

Lambert then tells the officers that he had taken cocaine. He asks: "Why you all trying to kill me?"

Instead of taking him inside, the officers put Lambert back into the patrol car, where it appears he is tased again.

MSNBC, which cited company device reports, reported that the three officers discharged their Tasers 20 times over roughly 30 minutes.

It's unclear how many of those discharges made contact, and CNN could not immediately confirm how many times Lambert was tased.

By the time officers arrived at a detention center several minutes away, Lambert was unresponsive. He was later pronounced dead at the same hospital he'd visited earlier with the officers.

The family disputes the medical examiner's report and puts the blame squarely on police.

Gwendolyn Smalls, Lambert's sister, told CNN's "Erin Burnett OutFront" that she would like to see the officers stripped of their badges, taken off the streets, and serve jail time for what they did.

"As you look at the video, it's excessive force. It's more than what was needed for a man who was restrained," she said.

And the acute cocaine intoxication?

"The amount of cocaine in his system was miniscule," said Messa, the attorney. "It was trace and not sufficient to be able to cause a sudden cardiac death, as opposed to the hundreds and thousands of volts of electricity that were sent through his body on multiple occasions that does cause sudden cardiac death."