Stroll around Mexico City's posh Polanco neighborhood during lunchtime and you can't miss them — small groups of physically imposing men typically dressed in grey or blue suits who are often making a bit of a show of attentively scanning their surroundings.

Hired to protect the nation's business and political elite from kidnappings, robberies, and assassinations, these bodyguards are a key part of the private security industry that is among Mexico's fast growing sectors. In recent weeks, however, they have also been hitting the headlines thanks to a string of incidents, ranging from the apparently trivial to the horrific, suggesting they believe themselves above the law.

"There's definitely an element of aggression among bodyguards these days, and I believe the sector needs better laws," says David Nieto, a 38-year-old powerfully-built former soldier who became a bodyguard after leaving the army in 2003. "I've had employers tell me that I had to get rid of someone who annoyed them, manhandle them. I tell them: if you're looking for a thug, ask someone else."

Soft spoken and polite, Nieto says he currently watches over an executive from a large foreign carmaker for a company that he says has "clear rules" about the use of force, handling discussions with people on the street, and generally what is and what is not allowed.

"But that's clearly not always the case," he admits of his profession.

Last year, local media reported that several people were killed in separate incidents involving bodyguards in Mexico City. In most of these cases, bodyguards shot and killed alleged robbers, though doubts over whether the show of force was excessive often remain.

These bodyguards, known as Guaruras, have also been linked to deaths that go beyond the heat of the moment. Last month the chief prosecutor in the state of Puebla, just east of Mexico City, announced that an investigation into the disappearance of six people had led to the discovery that a local businessmen had ordered their deaths in revenge for a violent burglary. According to the investigation the businessman sent out his bodyguards to abduct, torture, murder, mutilate, and then burn the victims.

Neither the murders in the capital nor the horror in Puebla, however, have received anything like the attention given to another incident that took place last month in the Miguel Hidalgo borough of Mexico City, where Polanco is located. The difference was that it played out live on Periscope.

The aggression involved a local government official called Arne Aus den Ruthen. His job is supposed to focus on roaming the area to identify problems with such things as garbage collection and broken street lights. He also seeks out traffic violators and other transgressors who he likes to film in the act and broadcast this live to his 50,000 followers.

He did just this on February 10 when he filmed four bodyguards as he berated them for parking their cars on the sidewalk. The increasingly agitated guards called their employer — a wealthy businessman and newspaper publisher with close ties to the federal government called Raúl Libién.

"Let me talk to that asshole," Libién was heard saying over the phone on the video. "Give him the cars so he can shove them up his ass!"

Video via YouTube

Nearby policemen stood by and refused to act, apparently intimidated by the bodyguards.

One week later, Aus den Ruthen apparently bumped into the same group that had again parked where they shouldn't. This time, however, bodyguards attacked him and took his cell phone. The film of this incident went viral.

"It's not just me, all citizens are in danger of being attacked by bodyguards who don't respect the law," Aus den Ruthen told VICE News a few weeks later. "The police apparently refused to act, so we need to continue to call out such behavior. There's no point in regulating if policemen are too afraid to deal with bodyguards and employers who violate the law."

Outrage at the arrogance of Mexico's business and political elite has been growing in recent years fueled by social media as citizens spread images of them, and their offspring, when they are drunk, abusive, aggressive, and disrespectful. Not infrequently those videos include threats to those doing the recording, or attempts to pull rank.

Bodyguards, critics say, are used as tools to enforce such threats, and often it works. Their employers' wealth and power often appears to be too daunting to police officers as in the Aus den Ruthen case.

"Politicians, businessmen and celebrities alike surround themselves with these arrogant types not just out of fear of being abducted, but also because they can exert power," political analyst Alfonso Zárate wrote in his weekly column in El Universal.

Zárate pointed to the sheer size of the problem.

"The numbers are worrisome from any point of view," he wrote. "Especially when we see that we are facing a kind of irregular army — dispersed, fragmented, informal — exceeding the approximately 544,000 making up the national police force."

According to a recent investigation by the news website Animal Político, the number of private security guards registered with the federal government has grown by over 17,000 per cent in a decade, from 419 in 2005 to 73,411 this year. Their employers have also proliferated in an impressive fashion. There were only 310 private security companies registered with the interior ministry in 2013. Now there are 1,103.

But it's not the registered companies and the guards they employ that worry critics the most, but rather those the federal authorities don't know about.

Animal Político cited estimates from the National Confederation of Private Security Firms (AMESP) putting the number of clandestine bodyguards at anywhere between a quarter of a million and 600,000. The group says the number of unregistered private security companies lies at around 8,000 or 9,000.

While those operating under the radar face no controls, even those that are registered are not properly regulated.

There are no requirements on the companies to check out potential bodyguards for hidden criminal records or to make them take drugs tests. The AMESP complains that instead companies face registration processes that are heavy on needless red tape.

Attempts to improve regulation have not got very far. A proposed National Private Security Law is stuck in the Senate. Mexico City's mayor, Miguel Ángel Mancera, gave few details and no dates when he promised he would introduce regulations that would make bodyguards and their vehicles more easily identifiable in the wake of the Aus den Ruthen incident.

One bodyguard involved was arrested and charged with aggravated robbery. The others have not faced any consequences. Nor has their boss, Raúl Libién.

The biggest impact of the alternation so far has been Mexico City's human rights commission ordering the city manager to stop filming after receiving complaints from people exposed by his Periscope broadcasts.

While many commentators recognize that such shaming methods used by an official do raise questions about abuse of power, some have pointed out that the primary issue in this case is that the employers of bodyguards are often more powerful than the state authorities.

"The problem is that we have used up rivers of ink talking about Arne and not about what to do about the hundreds of Libien who are on the loose," wrote Salvador Camarena in El Financiero. "Arne is a symptom, but the illness is that politicians and businessmen are untouchable jerks."

As he sipped coffee in an upscale cafe in Polanco, bodyguard David Nieto agreed — sort of.

"The laws are insufficient and regulation needs to be better," he said. "But that's ultimately the task of the government. You can't ask us bodyguards to regulate our own profession."