(CBS) — A 50-year-old man was critically hurt when he “stumbled” Thursday into the path of a Metra Rock Island Beverly branch train.

Authorities said the man was trespassing, walking alongside the tracks, which are not fenced, near 90th Street at about 4:10 p.m., when he “stumbled” into the path of the outbound train, which was slowing for a stop at 91st Street.  A liquor bottle was found next to the tracks.

Chicago Fire Department spokesman Larry Langford said that the man ended up under the locomotive, and that the cowcatcher on the front of the locomotive had to be jacked up in order to extricate the man.  He was transported to Advocate Christ Hospital in Oak Lawn in critical condition, with head and abdominal injuries.

Langford said authorities considered the incident an accident, and not intentional.

Metra spokesperson Meg Thomas Reile said some Beverly branch trains were rerouted onto the Rock Island District main line to keep service running.