A pilot repeatedly yelled out "Mayday" but did not say what the emergency was before his light plane crashed into the roof of an Australian shopping mall, killing himself and four American tourists, an accident investigator said Wednesday.

Police blamed "catastrophic engine failure" when a twin-engine Beechcraft B200 Super King Air crashed into the Direct Factory Outlet mall in the Melbourne suburb of Essendon on Tuesday moments after takeoff from a nearby runway.

But Australian Transport Safety Bureau chief commissioner Greg Hood said modern twin-engine aircraft are designed to continue flying if an engine failed.

"My understanding is he only used the word `Mayday' a number of times," Hood told reporters, referring to radio communication from pilot Max Quartermain to air traffic controllers.

"My understanding is he didn't refer to the specific nature of the emergency," Hood said.

Quartermain was the 63-year-old owner of the charter company Corporate and Leisure Travel.

The passengers were identified as Greg Reynolds De Haven, Russell Munsch, Glenn Garland and John Howard Washburn, who all lived in the Austin, Texas, area.

Quartermain was investigated by the Australian Transport Safety Bureau after a near mid-air collision that happened in September 2015.

Because of that incident, the Civil Aviation Safety Authority, the industry regulatory, required Quartermain to undergo proficiency tests to demonstrate he could fly a plane by instruments alone, authority spokesman Peter Gibson said. Quartermain passed those tests weeks after the near-miss, Gibson said.

Hood said he would not comment on Quartermain or his flying record. He added his flying record as well as the plane's maintenance record would be part of the crash investigation. Australian Transport Safety Bureau investigators are to compile a preliminary report within 28 days.

The bodies were removed from the wreckage on Tuesday, said Police Superintend Mick Frewen.

The busy shopping mall had yet to open for the day when the plane crashed after taking off from Melbourne's second-biggest airport at Essendon for a golfing trip to King Island, 255 kilometers (160 miles) to the south.

De Haven's sister, Denelle Wicht of Alexandria, Minnesota, said her brother survived dangerous work in the FBI and while serving in the U.S. Army during Vietnam only to die while enjoying retirement.

"He managed to get through all of that, to die this way," Wicht told The Associated Press.

She said the 70-year-old De Haven was "extremely athletic" and at one time aspired to become a pro golfer, but his young family at the time came first. After he retired, De Haven went on the senior pro golf circuit.

De Haven and his wife were part of a larger group that included at least two other couples who were touring Australia over the course of three weeks and intended to also see New Zealand, Wicht said.

She earlier told KXAN-TV in Austin that the men had chartered the flight for a round of golf on an offshore island. Their wives had stayed behind to pursue other interests.

Munsch was a founding partner in the Texas law firm of Munsch Hardt, which said in a statement Tuesday that he litigated some of the most prominent bankruptcy cases in the U.S., including the 2001 bankruptcy proceedings for Houston-based Enron Corp., one of the largest energy companies in the world before its collapse. He would have turned 62 on Wednesday.

"He could take something that's exceedingly complicated and boil it down and present it in a very simple way in court that was easy to understand," Rick Kopf, another founding partner of the firm, told the AP.

Munsch's neighbor, Washburn, was also a victim, his son, John Howard "Jay" Washburn Jr. said.

Meanwhile, an energy consulting firm in Austin confirmed that Garland, a former CEO and co-founder of the company, was also a victim in the crash. Garland was one of the founders in 2003 of CLEAResult and served as chief executive before retiring in 2015.

In a statement Tuesday, CLEAResult co-founder Jim Stimmel described Garland as a "visionary" when it came to finding efficiencies in producing and providing energy.

White House spokesman Sean Spicer said at a briefing Tuesday that President Donald Trump's "thoughts and prayers are with the families of the victims" and that U.S. Embassy and Consulate officials will provide assistance as the investigation progresses.