Five takeaways from our investigation into the world's largest private security company

Private security company G4S became a global juggernaut selling guards they tout as "the best in the security industry." The pitch has helped win the London-based company billions of dollars in public and private sector contracts all over the U.S., and its guards are posted everywhere – from nuclear facilities to gated communities.

But a USA TODAY/Milwaukee Journal Sentinel investigation found that G4S' carefully crafted image is undercut by a track record of employees committing acts of violence. In some cases, managers ignored or overlooked red flags.

The most infamous G4S guard, Omar Mateen, used his own weapons to kill 49 people and injure 53 more at Orlando's Pulse nightclub in 2016 while off duty. Although the Mateen case is unique, the company's failures to address troubling incidents during Mateen's G4S tenure are evident in other examples reporters uncovered.

In a series of written statements, G4S spokesperson Sabrina Rios said the company enforces strict policies to prevent hiring mistakes, including training for managers and a screening process that goes above and beyond what many clients and states require.

“Like all large employers,” Rios said in her statement, “there may occasionally be a very small number of employees who do not act in accordance with our procedures and policies.” She said there are limitations to what the company can and can’t find out before hiring guards. She said G4S officers save lives, prevent robberies and protect assets on a daily basis.

"The actions of a few former employees cited by USA TODAY are not representative of hard-working men and women of G4S," Rios said.

Here are five quick takeaways from the investigation:

The company's contracts in the US helped propel its growth

After entering the U.S. with its 2002 acquisition of security company Wackenhut, G4S grew into the third-biggest private employer in the world and won a large share of the security market. G4S armed a higher share of employees than its main competitors in the U.S. and took on business they wouldn't, such as juvenile detention centers and prisoner transport. The company in 2017 sold off its business interests in juvenile justice centers after a series of high-profile scandals involving allegations of abuse, sexual assaults and cover ups.

Managers have taken short cuts when they vet and hire

Employees have said in interviews, sworn testimony and state licensing reviews that they deviated from accepted screening, hiring and training practices. Some blamed pressure to make up costs from low bids and the subsequent turnover of employees caused by low pay. G4S representatives said wages are competitive in the industry and that managers who violate procedures are disciplined.

G4S hired or retained employees despite significant red flags

The company's guard force has included individuals with violent histories, veterans discharged from the military over psychiatric concerns and ex-law enforcement officers whose careers ended in disgrace. Some of them went on to commit crimes while working for G4S, including a former prison guard who assaulted a woman in the private office building he was guarding.

The company has armed mentally ill individuals

G4S typically issues its armed guards .38 Smith & Wesson revolvers. The company gave one of those guns to Devin Bailey, who had a documented history of severe mental illness and a warrant out for his arrest for assaulting a police officer, according to a lawsuit filed by his family. Bailey killed himself with the company's gun while stationed at a G4S guard post outside of a military hospital.

The lure of cheap security has been hard to resist for businesses and governments looking to outsource

G4S employees drive prison vans, stand guard at county jails and transport immigrant detainees for ICE – jobs that had once been handled by sworn law enforcement officers. However, G4S guards can make as little as $9.25 per hour, according to a job posting advertised earlier this month. Cities and businesses save millions by hiring G4S. When a California police chief asked the company to reduce wages to save another $44,000 on a contract to guard a jail, a G4S manager warned him that it would result in high turnover and less qualified guards. "We will take the lower cost," the chief replied in an email.

More in this series

A security empire deployed guards with violent pasts across the U.S. Some went on to rape, assault or kill

10 scandals at security giant G4S

Security giant G4S has lost hundreds of guns. Here’s where we found them

Takeaways from our investigation into guns lost by G4S, the largest security company in the world

G4S guards in Florida: lost guns, sex sting arrests and fired cops

This article originally appeared on USA TODAY: Security giant G4S put violent guards on patrol