A 20-year-old man is charged with attempted murder for allegedly beating a woman at random with a table leg on a St. Paul LRT platform during rush hour Tuesday — as several witnesses watched without intervening.

According to court documents filed in Ramsey County, the attack occurred at 5:45 p.m. on the METRO Green Line platform at Fairview and University avenues.

Officers arrived at the scene to find the 31-year-old victim "lying in a pool of blood, bleeding heavily from her head and face," the charges state, and "a large wooden table leg" was found nearby.

The suspect was soon found by officers a couple blocks west of the platform with "blood on both hands."

Court documents state surveillance footage showed the woman get off a bus and walk towards the platform. The suspect then jogged up behind her while "pulling up his pants with one hand … carrying the table leg with the other."

Footage then shows him striking her dozens of times, and continuing after she lost consciousness, according to the charges.

Surveillance footage also showed "a group of five or six male bystanders" walk up to the suspect, but no one stopped the attack.

"The bystanders did nothing to stop [the suspect] or hold him down — they let him slip away," the complaint states.

Two days later, the victim told investigators she didn't know her attacker, and she "saw joy in [his] eyes when he beat her up," the complaint states.

She suffered a skull fracture and required staples to close her head wounds, and one of her eyes was "completely swollen shut," according to court documents. She also suffered several fractures along her right arm "from her shoulder to her hand."

The complaint states the suspect is also charged with fifth-degree assault for allegedly punching a woman at random near the Hennepin County Government Center late last month.

The suspect, whose given address is Catholic Charities Hope Street Youth Shelter in Minneapolis, is being held in the Ramsey County Adult Detention Center.

He's charged with second-degree attempted murder and first-degree assault. He faces up to 20 years in prison if convicted.