A man in Las Vegas has died after police officers punched him, shocked him with a stun gun and used a controversial neck restraint to subdue him during an arrest outside a luxury hotel and casino on the Strip.

The Las Vegas Metropolitan Police Department said it is investigating the incident. The department hasn’t identified the man who died or the officers involved.

The American Civil Liberties Union of Nevada blasted the police response, saying “chokehold practices must stop.”

“Too many people have died as a result of this type of excessive force,” Tod Story, executive director of the ACLU of Nevada, told NBC 3. “And too many questions remain about the use of chokeholds by our police.”

The encounter began around 1 a.m. on Sunday when the man approached two uniformed officers inside the Venetian Hotel, according to police.

Police said the man was “acting erratic” and told the officers there were people “chasing him.” The Associated Press and the Las Vegas Review-Journal reported that he was unarmed.

When one officer tried talking with him, the man darted out of the hotel. The officers followed him to the rear of the building, police said, where they saw the man trying to open the tailgate and driver’s side door of a pickup truck.

One officer used a stun gun on the man, according to police. Though it had an “immediate effect” on him, police said, the man continued to “fight with officers despite the attempts made to take him into custody.”

Venetian security guards soon arrived. As the fight escalated, police said, one officer hit the man multiple times with a closed fist, then used a chokehold-like technique called a lateral vascular neck restraint to control him.

The man fell unconscious, at which point the officers performed CPR, according to police. He was transported to the Sun Trauma Center, where he was pronounced dead at 1:39 a.m.

A spokesman for Las Vegas Sands, which operates the Venetian, didn’t immediately respond to messages seeking comment Monday morning.

Techniques like the lateral vascular neck restraint have come under intense criticism in recent years, particularly since the 2014 death of Eric Garner, an unarmed black man from Staten Island who died after a police officer put him in a chokehold. Captured on cellphone video, the 43-year-old father said “I can’t breathe” 11 times before he died of neck and chest compression, made worse by his underlying health problems. Activists around the country adopted the phrase as a rallying cry.

The lateral vascular neck restraint is not considered deadly force by the Las Vegas police. According to the department’s general orders, all commissioned officers at or below the rank of lieutenant are trained in the technique, which is described as a “defensive tactic to quickly and safely stop active/aggressive resistance.”

The restraint, used by police departments around the country, is designed to restrict blood flow to a person’s brain by compressing arteries in the neck, rather than by cutting off a person’s airway. Deployed properly, it’s supposed to help officers control suspects without killing or seriously injuring them, according to the National Law Enforcement Training Center.

The organization calls neck restraints “a safe, viable and effective option for police officers in arrest and control scenarios.” It also stresses that the lateral vascular neck restraint is different from a chokehold or bar-arm choke, which involve squeezing a person’s trachea.

Just last week, Las Vegas police reported that use of deadly and non-deadly force by its officers had decreased in recent years. In 2016, the department had 10 officer-involved shootings, the lowest number in 20 years, according to the department’s annual use of force report. Non-deadly use of force decreased by 8 percent over the past five years, the report said.

Speaking to local media last week, Undersheriff Kevin McMahill said: “Our officers are trained to exhaust all of their options before resorting to the use of deadly force.”

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