We are hearing the descriptive new 911 calls after a man, who was thought to be high on the designer street drug flakka, held up a South Florida gas station.

That man, Markus Clark, 26, later died in custody.

What happened at the Exxon gas station near Fort Lauderdale Wednesday night is now the center of an investigation at the Boward Sheriff's Office.

Deputies say it all started when Clark tried to rob the business, his bizarre behavior was caught by surveillance cameras.

Clark is seen behind the counter in contact with the clerk, who then called 911.

Dispatcher: "OK sir, sir listen. How did he try to rob you sir?"

Caller: "Yeah, he got inside the register area, he locked my door. Now he’s doing something. He’s pretending like he’s sick but I think he’s well."

Deputies said Clark was showing signs connected to the new street drug flakka. Investigators say it's dirt cheap, selling for just $5 a pop and the high causes people to exhibit excessive strength.

Surveillance video showed deputies as they responded to the 911 call from the gas station. Three deputies were seen trying to hold Clark down.

Officials say it took several deputies to subdue and handcuff Clark. Once they got him in custody, he was rushed to the hospital.

"And when they got to the hospital and took his temperature it was 106.3, so I mean literally someone on fire melting inside," said BSO spokesperson Veda Coleman-Wright.

Clark died the next morning. As detectives continue to investigate his death, the medical examiner's office will also conduct an autopsy. The results could take weeks before they are released.