BROCKTON — According to police, he was the last person to have seen a Brockton mother and her toddler son alive. He was wanted by police in two states on charges of kidnapping and assault. He escaped on a flight to Ecuador.

And no one knew his real name.

The challenge of finding Luis Guaman – also known as Segundo Castro and Antonio Castro – was heightened by the fact that he lived, worked and traveled in a shadowy world, without a Social Security number, driver’s license, work visa or green card.

“The multiple identities and dates of birth have made it enormously frustrating for investigators to determine who he was and where he was,â€