A 24-year-old man who died after being restrained and pepper sprayed at a Detroit-area mall on Tuesday lost his life because of the actions of security guards, his attorney told The Huffington Post.

Mackenzie Cochran was standing outside a jewelry store "suspiciously" at Northland Mall in Southfield, Mich. Monday afternoon before security told him to leave. Cochran returned to the mall the next day, authorities said, apparently threatening to kill someone, the Detroit News reported.

When security guards from the mall took down Cochran and restrained him, a cell phone video obtained by WJBK-TV shows that Cochran began to yell for help, saying that he couldn't breathe (see above). He was transferred to a nearby hospital, where he was pronounced dead.

Using pepper spray is known to cause respiratory distress, said attorney Gerald Thurswell, who has been retained by Cochhran's family. That distress was compounded when a security guard put Cochran on the ground chest-first, then placed his left knee on Cochran's back.

"He calls out five or six times, saying that he can't breathe and they don't take the knee off his back, they keep his knee compressed," Thurswell told The Huffington Post. "He says, call the paramedics, he says he's going to die, call 911, they keep him down. They say, if you can talk, you can breathe. Finally, when he can't talk and he can't breathe, and he's totally passed out, they finally take the knee off his back."

"For all practical purposes, he was dead," Thurswell added.

An autopsy determined there were no signs of trauma on Cochran's body. A toxicology screen to test for drugs and alcohol in the victim's body will take several weeks, the Detroit News reported.

Thurswell confirmed that a witness to Cochran's death, Akil Copeland, was giving a statement to Southfield police. Copeland told WJBK that he had offered to give Cochran CPR at the mall before his death but security guards refused his help.

"They told me that I was being troublesome, I was causing a problem by asking for the man's well-being," Copeland told WJBK. "I don't know, maybe I could have saved him."

Cochran lived with his mother and sister in the nearby suburb of Ferndale. Thurswell said he was trying to finish his high school GED and had three classes left.

The guards acted as "judge, jury and executioner," Thurswell said, noting that the guards could have kept Cochran restrained and in handcuffs, but still lifted the knee from his back and provided him with oxygen when he screamed that he couldn't breathe.