The death of a Ewing High School senior has been ruled an accident.

Alex Martinez, 18, was struck by a CSX freight train on a rail bridge over the Delaware River Friday. The Mercer County Medical Examiner's Office told NJ Advance Media his death was accidental following an autopsy.

Martinez's girlfriend, Bianca Russo, told New Jersey 101.5 Martinez often traveled the bridge to get to her home in Morrisville, Pa.

"Someone that was working on the tracks told him (Thursday) that he needed to get down because he's not supposed to be up there," Russo said.

He was back on the tracks on Friday. Russo said she thought he was probably wearing headphones, and apparently couldn't hear the train pulling 28 cars approaching from the north.

"The train vibrates and it's pretty loud, and the train hit him from the back," Russo said.

Spokeswoman Casey DiBlasio said the Mercer County Prosecutor's Office is not involved with the investigation into the incident.

"His world consisted of his family first, his 'boys,' his 'Mula'/work, and his school. Alex LOVES everyone and he'd do anything to help the ones around him. From taking people's garbage out, walking their dogs, to shoveling snow, Alex is always that helping hand. Alex is one of a kind. He made a positive impact on everyone's life he entered, everyone loves Alex," friend Cierra Ashley wrote on a GoFundMe page she created for Martinez's family.

Funeral arrangements for Martinez have not been announced.