An 18-year-old man was charged Thursday with attempted murder after he allegedly shot a good Samaritan who was trying to stop a robbery at a St. Paul light-rail station.

Treheem Smith, of St. Paul, was charged in Ramsey County District Court with second-degree attempted murder in the shooting last week. Authorities said that Smith shot a 30-year-old man who had tried to intervene on behalf of a vulnerable man under assault by others.

As of Thursday, the shooting victim was listed in critical condition at Regions Hospital.

Two other boys, ages 14 and 15, have pleaded guilty to first-degree aggravated robbery in connection with this case.

"This is a tragic case of a man who is shot coming to the aid of a crime victim," said Ramsey County Attorney John Choi in a statement. "We will do everything in our power to seek justice for the victim."

According to the complaint and police reports, St. Paul police responded around 10 p.m. on Sept. 2 to a call of a man being assaulted by four males on the light-rail platform at University and Western avenues.

During the incident, four people — the shooting victim, his 11-year-old daughter and two friends — pulled over in a car and tried to stop the assault with honks and shouts.

The shooting victim and a friend ran at the platform, but the victim was shot before he could get there. He returned to the car, and his girlfriend drove them to the hospital.

Video of the incident shows a man on the platform with a backpack and four teenage boys in a group talking. One of the juveniles on a bike rides by the man, kicks him in the head and appears to take a backpack.

Later in the video, another man approaches the teens, who ran, and the man is shot.

Smith told police that as he walked to the train station he saw a man who looked drunk and saw people fighting with the man, who he said was using racial epithets. Smith said he heard a car honking and then yelling, and saw people running from the platform.

Smith said a man walking down the street approached and punched him. He responded by pulling out his gun and firing twice, hitting another man near the station. Smith said he ran away and later threw the gun into Lake Phalen.

Nicole Norfleet • 612-673-4495

Twitter: @stribnorfleet