It's been a year of crippling emotion for Cindy and Paul Tarashuk — a year since the death of their 26-year-old son also named Paul.

"Talking about him gets me really upset," Cindy Tarashuk told CBS News. "Talking about this stuff gets me angry."

Paul Tarashuk had schizoaffective disorder, suffering delusions and hallucinations. But he was getting on with his life, until one night last September, when he had a psychotic breakdown traveling along a highway in Orangeburg County, South Carolina.

Parked for a roadside break, a trucker suddenly saw Tarashuk walk toward him, naked. The trucker took off, but as he drove down the interstate, he realized Tarashuk was riding on his rig and called 911.

Paul Tarashuk, left, with his father Paul. Tarashuk family

Officers from three different law enforcement agencies responded, including Orangeburg County Sheriff's Deputy Clifford Doroski, who was certain Tarashuk was high or drunk.

Doroski's body camera recorded what happened when EMS arrived. They asked Tarashuk if he spoke English. He didn't answer the first responders who berated and cursed at him.

"I'm being f***ing serious. I'm sleepy. Give me your damn name so I can go home for real. I'm tired," one first responder said.

They shoved an ammonia capsule up his nose. He didn't flinch.

"There, I mean at that point, someone should have stepped up and said 'We gotta take him in some place. He's not just someone to let go,'" said Paula Tarashuk.

As troubling as it is to watch how the ambulance crew treats Tarashuk during the call, it's even more disturbing to watch the sheriff's deputy after.

The deputy put Tarashuk into his cruiser and drove him 15 miles to a closed gas station near the county line. Surveillance video outside the gas station captured Tarashuk the last time he was seen alive. He had no shoes, no phone and no idea where he was.

"It's just watching him walk to his death. He was escorted by an officer to his death," Cindy said.

From there, Tarashuk ended up back on the same highway, where he was hit by a car. Nearly five hours later, the same EMS crew was called to deal with Tarashuk again. But this time, he was dead.

"If I'd have known that he was just going to drop him off, we'd have just took him to the hospital and dropped him there," one of the first responders was heard saying.

A toxicology report from the Orangeburg County Coroner's office came up clean. Despite this, Deputy Clifford Doroski is still on the job, and so is one of the EMTs.

"I think there needs to be a better investigation into what happened. I mean we can see it on the video. I think somebody, you know, needs to explain to them why it happened, which they haven't," said State Sen. Katrina Shealy.

CBS News asked both the sheriff's and EMS departments for on camera interviews. They both declined, citing an ongoing investigation. After a state investigation, one of the EMTs was fired.

"They didn't do their job. That's it," Cindy said. "They just didn't do their job. They didn't care enough about human life to do their job."

The Tarashuks have set up a Facebook page to bring attention to their son's case. On Wednesday, the family filed a civil suit against the department and individuals involved.

Editors Note: The South Carolina Attorney General contacted CBS News after this story aired and offered this statement: "While we can't comment on this specific case, our opinion says that the law does contemplate scenarios in which law enforcement can be prosecuted criminally for not protecting vulnerable adults. This case is currently being investigated by the State Law Enforcement Division and after that is complete a decision on the specifics of this case will be made."