A young man killed Monday evening when he stopped to help three snowmachiners stuck on the Parks Highway was a University of Alaska Fairbanks student known for making fast friends.

Alaska State Troopers said Sylvester Smith, 22, was killed south of Nenana near Mile 280 of the Parks Highway. Troopers got a report just after 6 p.m. of a pedestrian who had stepped out of his vehicle to help a disabled snowmachiner, only to be hit by a tanker truck.

Smith was a senior majoring in petroleum engineering at UAF, which he had attended since fall 2013, according to university public information officer Marmian Grimes. He also worked on campus at the Office of Information Technology, she said in an email.

Professor Abhijit Dandekar, chair of the petroleum engineering department, described Smith through Grimes as "one of the most polite, respectful and hard-working students" he has taught.

Troopers were still investigating the crash and trying to determine where Smith was standing when he was hit, spokeswoman Megan Peters said.

Smith had been heading north in his 2016 blue Ford Fiesta, which wasn't struck, Peters said. He appears to have turned on his hazard lights before stepping out to help, she said.

Three snowmachiners were trying to cross the highway after riding on the Rex Trail, she said.

"They stated they lost traction on the pavement and were working on getting their sleds out of the road when the collision occurred," she said.

Robert Smith, 65 of Anderson, was driving a tanker truck full of methane, troopers said. He told troopers he couldn't stop and went into the ditch to try to avoid a collision, Peters said.

The Smiths are not related. Sylvester Smith died at the crash site, troopers said. The truck driver wasn't injured. Officers who enforce commercial motor vehicle laws also went to the scene.

Sylvester Smith was from a tight-knit Anchorage family, who weren't ready to talk about what happened, said friend Scott Lamken of Pinedale, Wyoming.

"Right now they are just trying to hold it together and are having a hard time doing that," Lamken said.

Lamken met Smith a year ago after another tragedy. Lamken's daughter, also a UAF student, died suddenly in November 2016. The two young people had been friends since they were freshmen, and Smith stepped up to help Lamken at a rough time.

"He was a great kid," Lamken said. "He would give you the jacket off his back in the middle of November, which is what he did." It was 25 degrees below zero in Fairbanks, and Lamken said he had never experienced such cold.

They started talking and texting regularly.

"I consider him one of my family members. I wanted to bring him out here for my niece's wedding," Lamken said.

Smith made friends easily and nurtured relationships, Lamken said.

His Facebook feed is checkered with funny videos and also with posts about his beloved car and life in Fairbanks.