Only four seconds elapsed from the time the two engineers could have seen each other around the curve in Chatsworth where the Metrolink commuter train and a Union Pacific freight train collided head-on Friday. The UP engineer applied brakes — futilely — but Robert M. Sanchez never did, the NTSB says. Sanchez worked a split shift that day for Metrolink, starting about 6 a.m., going off at 9:26 am, then resuming work at 2 p.m., the New York Times reports. The train's conductor was interviewed, and the scenario reenacted on the tracks, as the NTSB continued Tuesday to fill in what it knows about Sanchez and the crash that occured after his train did not stop at a red signal. Points from the NYT, Conan Nolan's report on KNBC or a Los Angeles Times profile of Sanchez:

• Both the freight and the Metrolink train were traveling about 40 miles an hour, hence the terrific collision that witnesses described as like a bomb going off.
• An autopsy is being conducted on Sanchez's remains. A former friend said that Sanchez took diabetes medication, but no other health issues are known.
• The NTSB said Sanchez was hired by Union Pacific in 1996. In 1998, he went to Amtrak, then was hired by a contractor to work for Metrolink in 2005. No reason for the job changes was discussed Tuesday.
• Sanchez was described as withdrawn since his male companion, who was HIV positive, hanged himself at their home in Crestline in 2003. Sanchez lived alone in La Crescenta with four Italian greyhounds when he died.
• Sanchez served 90 days in jail for shoplifting after a 2002 arrest.
• NTSB board member Kitty Higgins said the agency would look into a news report that Sanchez was involved in a fatal crash with a pedestrian earlier this month.