A man was fatally shot by an officer as he mauled up to 80 percent of another man's face in Miami, the president of the Fraternal Order of Police told NBC 6 on Sunday.

Miami Fire Rescue said that man suffered trauma to his face and was bleeding heavily when they arrived. He was rushed to Jackson Memorial Hospital, where he remained in serious condition, officials said.

"Seventy-five to 80 percent of his face was missing, and he was actually swallowing pieces of the man's face," said Armando Aguilar, president of the Fraternal Order of Police, Lodge #20.

Neither man nor the police officer have been identified. The attack occurred on a pedestrian bridge just off a MacArthur Causeway exit ramp on Saturday afternoon.

Parts of the confrontation were caught by The Miami Herald's surveillance camera, which overlooks the crime scene. A witness said he couldn't believe what he was seeing during the Saturday attack.

"He bite him here, here," said the witness who identified himself as Eric. He grabbed at his own cheek and neck to demonstrate.

The veteran Miami Police officer who responded told his superiors that he pointed a gun at the attacker, who was naked, and asked him to stop.

"He growled at him like a wild animal and kept eating at the man's face," Aguilar said.

City of Miami Police say the officer had no choice but to shoot the man. His wild behavior was symptomatic of excited delirium, Aguilar said. The disorder is usually drug-related and can incite violence, unexpected strength and even hyperthermia.

"Inside their body their organs are burning up alive. They've reached temperature where their actually burning up, and it actually makes them take off their clothes," Aguilar said.

The website exciteddelirium.org has uploaded video examples of people experts believe to be suffering from the disorder.

There have been four recent cases in Miami-Dade County including one with 21-year-old George Salgado, Aguilar said. In April, police said they had to use a stun gun on Salgado because of his aggressive behavior. A 911 caller describes his encounter with Salgado to the operator.

"There's a naked man, and he's aggressive. He tore my clothes and tried to bite my neck," the caller said in Spanish. A medical report showed Salgado had taken three stamps of LSD.

But in Saturday's case, police believe the officer saved the man's life by shooting the attacker before he could harm him even further.

"There's no doubt in my mind. The man would be dead right now," Aguilar said.

Police urged any residents that witnessed the incident to contact them at 305-471-TIPS.

Jackson Memorial Hospital's emergency room has seen an increase of people suffering from psychosis caused by a variety of drugs.

“Cocaine and new LSDs, they cause delirium, which (means) you don't make sense when you take them," said Paul Adams, an ER doctor at Jackson Memorial Hospital. "And when you don't make sense and you don't control your emotions, you don’t control your actions, you find yourself in circumstances that you just don't want to be in.”

Dr. Adams said he has seen the effects of a designer drug nicknamed "bath salts" – which also causes body temperatures to spike – during and after the recent Ultra Music Festival.

"People don't drink water while they're taking it so they become dehydrated. So you mix dehydration with elevated temperature with loss of inhibitions, and you have a life-threatening combination. Mix for disaster," Adams said.

Bath salts were banned in Florida in 2011, but new formulations have become dangerously popular.

“We've had several deaths. Earlier last year we probably saw our first deaths from bath salts, where people (were) running onto MacArthur Causeway, under MacArthur Causeway, being chased by the police and then all of the sudden just collapsing," Adams said.