LAS VEGAS (AP) -- President Donald Trump plans to travel to Las Vegas on Wednesday to speak with law enforcement officers and the survivors of a concert shooting outside the Mandalay Bay hotel casino that killed 59 people.
The visit comes as investigators continue pursuing leads to learn a motive for the attack Sunday by Stephen Paddock, a 64-year-old high-stakes gambler and retired accountant who had no known history of mental illness.
More about the deadliest mass shooting in modern U.S. history:
The Las Vegas gunman's girlfriend will be at the center of the investigation into the shooting deaths of 59 people as authorities try to determine why a man with no known record of violence or crime would open fire on a concert crowd from a high-rise hotel.
Marilou Danley, 62, was in the Philippines at the time of the shooting. A law enforcement official says FBI agents met Danley at the airport in Los Angeles late Tuesday night.
The official wasn't authorized to publicly discuss the matter and spoke to The Associated Press on condition of anonymity.
Paddock opened fire on a country music festival on Sunday. He died of an apparent self-inflicted gunshot wound to the head.
Authorities have not discovered a motive.
Authorities revealed Tuesday that Paddock stuck a camera inside the peephole of his hotel room to see down the hallway as he opened fire on a crowd of concertgoers. Undersheriff Kevin McMahill said Paddock set up two cameras in the hallway outside his room so he could watch law enforcement or security approach.
Federal officials also said Paddock had devices attached to 12 weapons that allow semiautomatic rifles to mimic fully automatic gunfire. In all, he had nearly 50 guns in three locations, authorities said.
The victims included a man celebrating his 23rd wedding anniversary, a UCLA nurse and a California firefighter.
Sunrise Hospital and Medical Center said an additional person died Tuesday afternoon. But the death toll remained at 59 after Clark County Coroner John Fudenberg revised his earlier count of victims downward by one.
More than 500 people were injured in the attacks. Forty-eight of them, including a 16-year-old boy and a 17-year-old girl, remained in critical condition Tuesday night, hospital officials said.
So far, neither law enforcement nor Paddock's relatives have been able to explain what motivated a multimillionaire with no apparent criminal history to commit mass murder before killing himself.
Retired FBI profiler Jim Clemente speculated that there was "some sort of major trigger in his life — a great loss, a breakup, or maybe he just found out he has a terminal disease."
He also noted a possible genetic component to the slaying: Paddock's father was a bank robber who was on the FBI's most-wanted list in the 1960s and was diagnosed as a psychopath.
Paddock transferred $100,000 overseas in the days before the attack, a U.S. official briefed by law enforcement told The Associated Press. Investigators are trying to track that money and are also looking into at least a dozen financial reports over the past several weeks that said Paddock had gambled more than $10,000 per day, the official said.
President Donald Trump is headed to Las Vegas on Wednesday to meet with survivors and law enforcement officials.
Trump will be joined on the trip by first lady Melania Trump. He promised to offer his "personal respects and condolences to everybody" in the time of grief during his visit.
Speaking to reporters Tuesday as he departed on a trip to Puerto Rico, Trump called the gunman "demented" and a "very, very sick individual."
Vice President Mike Pence, in Phoenix to tout the administration's tax overhaul plan, stopped to donate blood Tuesday to raise awareness of those in need after the Las Vegas shooting.
A vigil was held in Orlando on Tuesday evening for the victims of the Las Vegas attacks, which surpassed the Pulse nightclub shooting as the deadliest mass shooting in modern U.S. history.
A nearby church rang its bell 59 times, once for each of the people killed in Sunday's shooting.
Pulse nightclub owner Barbara Poma said the Vegas shooting takes Orlando back to June 12, 2016, when a gunman killed 49 people and wounded 58 in her gay nightclub in what was then the nation's deadliest mass shooting.
Several hundred people also turned out for a vigil in Philadelphia on Tuesday that was attended by Democratic Gov. Tom Wolf as well as church and synagogue leaders.