NTSB Tuesday provided a transcript of text messages to and from operator Robert Sanchez, who was killed as his train ran a red signal and collided with a Union Pacific freight train. The messages reveal that Sanchez had allowed one text-message correspondent to ride in the locomotive cab a few days before the incident.

Officials said Sanchez sent and received 57 text messages while on duty that day, including one sent by him 22 seconds before his train collided with the UP consist. NTSB said there was no sign of mechanical error involving the Metrolink train.