[El Cid]

Muslim convert?

Unlikely. If you yahoo search the engineer's background, you'll find that he was carrying a lot of 'baggage'. Or as someone else put it, his worries were comparable to that of a fat mouse in a house of hungry cats.
Concerned about losing his job due to a string of thefts he had committed and been caught. His H-IV positive partner recently committed suicide. The sister of said partner was convinced that her brother was not suicidal and was dropping hints that she was 'off'd' by someone (i.e., the engineer)... Just an all-around unseemly story. He may have just 'snapped'. Very tragic for very many people.

[El Cid]

Re: 15

proof-read three times next time...

that she he was 'off'd'

[GOP Poet]

Also add to this that elderly lady that he just decided years ago to be friendly with (even he mentioned she thought it was a bit odd with the age difference and all.) for the first time told him she was unable to meet with him (off the cuff--he called out of the blue and wanted to get together, but it wasn't enough time for her to get ready so she said, "no.") and he was uncharacteristically gruff and cold with her when she said no. This is the last time she spoke with him.

I think a case could be made that this was a suicide/homicide. Regarding the old partner that 'hung' himself. It might be worth it to reopen the case as a double check that it was not a murder. Whether or not the engineer is responsible for his ex-partner's death, he still could have committed a murder-suicide with the Metrolink. He sounded a bit like a mental case.