A man accused of murder in California appears to have sought a marriage license with a woman charged in connection with the fatal shooting of a U.S. Border Patrol agent in Vermont. The woman, Teresa Youngblut,

Federal prosecutors say a Washington state woman charged in connection with the fatal shooting of U.S. border patrol agent in Vermont had been in frequent contact with someone whom authorities have linked to homicides in Pennsylvania and California.

As the sprawling investigation unfolds, here’s an overview of the key figures involved and their alleged connections.