Michigan resident Jason Dalton, the alleged shooter in a spree Saturday night that resulted in six deaths and two injuries, is 45 years old and had worked as an insurance salesman for Progressive. He was also an Uber driver. Amidst his shooting, Dalton reportedly picked up Uber riders in Kalamazoo, Mich.

Uber is playing defense now, with chief security officer Joe Sullivan saying on Tuesday: "No background check would have flagged and anticipated this situation." Still, the company has acknowledged that Dalton passed its background check, and also that it received complaints about Dalton hours before the shooting.

The event has raised obvious questions about Uber's safety measures for passengers and its process for approving drivers, who are not considered "employees" but contractors. They are questions that have been raised time and again as Uber has been in the news for the wrong reasons, and they are questions that a P.R. statement is unlikely to put to rest. This is the latest in a long line of scandals, missteps, and criminal activity associated with the app. Earlier this month, Uber spent nearly $30 million to settle two lawsuits over misleading customers regarding its safety measures.

But Uber continues to raise venture capital at soaring valuations: In July, the company closed a new round of more than $1 billion, bringing its valuation to more than $50 billion and leap-frogging Xiaomi, the Chinese smartphone maker, as the world's highest-valued tech "unicorn." (Airbnb, Snapchat, Palantir and other companies valued at more than $10 billion are now called "decacorns," but at $50 billion, Uber is a lone "quinticorn." In December, tech outlets reported Uber is seeking another couple billion in funding that would value it above $60 billion.) The company is like Donald Trump, in a way: Seemingly no amount of bad press can slow its momentum. The app now delivers an average 2 million rides every day.

From passengers being raped by Uber drivers, to the app implementing surge pricing during a hostage situation, to a senior executive suggesting the company dig up dirt on journalists, here are just some of the worst moments the six-year-old company has weathered.

December 2013: Uber driver hits a family, killing one



An Uber driver in San Francisco, Syed Muzaffar, struck a family in a crosswalk, killing a 6-year-old child. The family sued Uber for wrongful death, and the company at first denied responsibility because Muzaffar was in between fares at the time of the accident. The accident was the first to ignite a still-ongoing debate over whether Uber can be held accountable for its drivers, who are contractors, not employees. Last year, Uber settled with the family for an undisclosed sum.

January 2014: Uber employees order fake rides to sink competitor



Citing leaked documents, multiple outlets reported that Uber employees had conducted an organized effort to order cars from a new competitor app, Gett, and cancel their orders just before the ride arrived. Later, reports would emerge of a much more concerted effort by Uber to do this again to its competitor Lyft.

February 2014: Uber CEO Travis Kalanick gets unflattering profile in GQ



In a profile that ran in GQ, Kalanick is on the record calling his ride-sharing app "Boob-er" (a reference to his attracting more women thanks to the app's success) and blaming the media for suggesting Uber is "somehow liable" for various incidents of bad behavior by drivers. It was not a flattering piece.

March 2014: Uber driver accused of groping a passenger



A passenger in Chicago sued Uber after her driver, Jigneshkumar Patel, allegedly locked the car and groped her before letting her out. Uber deactivated the driver's account immediately after the incident and said "the safety of riders and drivers comes first."

June 2014: Uber driver kidnaps woman

An Uber driver in Los Angeles, Frederick Dencer, was arrested after kidnapping a woman who had passed out in the car. The woman woke up in a hotel with the driver, who asked her to stay but allowed her to leave. He was eventually released without charges.

June 2014: Uber driver charged for assault

A cab driver in San Francisco, Daveea Whitmire, was charged with battery in two different assault incidents with passengers, one of which occurred when he was driving for Uber. The charges in the Uber incident were later dropped, but the story raised concerns over how the driver could have passed Uber's background check in the first place because Whitmire had felony charges from 2009 and 2012 for selling drugs.