Armen Azatian was surfacing from a spearfishing dive in Monterey Bay when he heard a bloodcurdling scream, DailyNews reported.

It was his 25-year-old son, who had just fought off what he said was a great white shark that ripped into his thigh and lower leg.

The elder Azatian didn’t witness the attack, but realized immediately something catastrophic had happened — his son had never cried since he was a baby.

“It was like lightning struck my head and it was cracking,” Armen Azatian of Northridge said, as he recalled the attack and its aftermath on Sunday while his son underwent a second surgery to repair his badly damaged leg.

“It was horrifying; his muscles were torn apart,” said Azatian, a psychiatrist who worked for a year as a surgery intern but had never seen anything as gruesome.

Grigor Azatian was spearfishing with his dad. While his dad went off in search of prey, Grigor took photos with an underwater camera, then dove in again with his spear. It was then he saw the great white — and, he told his dad, the shark saw him and appeared to swim away.

Grigor surfaced to warn his father of the shark, and while he scanned the water waiting for his dad to surface, the shark returned from behind and attacked.

“The shark grabbed him and didn’t let him go, and took at least two bites” — mid-thigh and below the knee, Armen Azatian said his son told him. “He tried to fight with the shark. I don’t think he could do much, maybe pushing, moving his legs.”  Grigor had lost track of his spear, and couldn’t reach his knife, which was strapped to the leg near the shark’s mouth. But he punched the shark’s face and kicked. At one point, the creature’s nose rose above the water, and he looked into its left eye.

He managed to free himself, screaming, then swam about 20 yards to the dinghy. His father surfaced about 30 yards away and reached the boat shortly after.

Laying with his mangled leg in the boat, Grigor asked that his constricting wetsuit be cut open — then directed his father in how to undo the lock on his knife.

“He was very calm,” Dr. Azatian said. “He just said he cannot breathe well.” His dad grabbed a float line and wrapped a tourniquet around his son’s leg.

After the attack, Grigor underwent a two-hour surgery.

A surgeon emerged and said he was guardedly optimistic, and that Grigor had not suffered great tissue loss. One of his muscles, the long, thin sartorius that runs down the thigh, remains at risk.

Despite the severe wounds, Azatian contemplates how much worse it could have been.

“That shark might have dragged him down,” he said. Those sharp teeth might have hit a major artery, or taken a bigger hunk of muscle. A bite that grazed his arm might have gone deeper.

The second surgery Sunday was successful, Azatian said, and another will be performed later this week.