Stephen Paddock, the man who gunned down 58 people in Las Vegas on Sunday night at Mandalay Bay Resort and Casino, had set up cameras around the hotel that he used during the attack, the Las Vegas police have said. The attack has been described as the “worst mass shooting” in recent United States history.

Clark County Sheriff Joseph Lombardo said the shooter had installed cameras both inside and outside his room to monitor if security were approaching him, BBC reported. Two cameras were set up in the hallway and one in the peephole, Lombardo said.

“It was pre-planned extensively and I am pretty sure he evaluated everything he did in his actions,” BBC quoted Lombardo as saying.

The sheriff said the Federal Bureau of Investigation was looking into all digital and electronic evidence obtained from the hotel.

Paddock had continuously fired on the crowd for nine minutes before a SWAT team reached his room at Mandalay Bay Hotel, The Independent reported. The 64-year-old is then believed to have killed himself before the officers could reach him.

More than 500 were injured after Paddock opened fire at people attending the festival. President Donald Trump called the shooting “an act of pure evil”.