Bloodthirsty madman Stephen Paddock sprayed 200 rounds at a hotel security guard who amazingly dodged serious injury from that barrage of bullets, authorities said Wednesday.

The Mandalay Bay guard was feet away from cops when he spotted a 32rd-floor room door, slightly ajar, and approached — drawing fire from Paddock inside at 10:18 p.m. Sunday, Clark County Sheriff Joseph Lombardo revealed.

“It’s amazing that that security guard didn’t sustain additional injury,” Lombardo said.

Even after the guard and cops retreated, the wounded security man refused to leave the scene and kept going door to door with his master key to evacuate guests, officials said.

“His bravery was amazing because he remained with our officers … and continued to help them clear rooms until our officer demanded he seek medical attention,” Lombardo said.

Police said they’re still struggling to piece together Paddock’s motive for carrying out the worst mass shooting in US history — killing at least 58 people and injuring 489 on Sunday night.

Earlier estimates had the wounded total at more than 500, but officials said Wednesday that inflated number came from confusion and patients being accidentally counted twice in the hours following Sunday night’s mayhem.

Lombardo called Paddock “disturbed and dangerous” but stopped short of assigning a motive.

There was no suicide note found inside his hotel, where Paddock blew his brains out before cops got to him.

“Stephen Paddock is a man who spent decades acquiring weapons and ammo and lived a secret life, much of which will never be fully understood,” Lombardo said. “He meticulously planned the worst domestic attack in United States history.”

Clark County’s top cop said he still believes Paddock must have had some help along the way.

“Because look at this, you look at the weapon, obtaining the different amounts of Tannerite (explosives) available, do you think this was all accomplished on his own?” he said.

“You got to make the assumption he had to have some help at some point.”

Authorities revealed Wednesday night that they found 1,600 rounds of ammunition and 50 pounds of explosives in Paddock’s car.

Police also mapped out the most detailed timeline yet of Paddock’s attack on concertgoers at the Route 91 Harvest Festival.

Paddock opened fire at 10:05 p.m. and squeezed off his last rounds at 10:15 p.m., police said.

In between, cops arrived on the 31st floor — just below Paddock — at 10:12 p.m. and got to the shooter’s 32nd floor at 10:17 p.m., officials said.

Cops and the wounded security guard kept clearing that 32nd floor as more police amassed around Paddock’s room — taking their time because he was not firing, Lombardo explained.

SWAT officers set off explosives to clear the way into Paddock’s lair at 11:20 p.m. and found his lifeless body — though it wasn’t clear when the madman took his own life, authorities said.