A Washington state woman has been ordered held without bail in connection with the death of a U.S. Border Patrol agent in Vermont.

At a hearing and in court filings, a federal prosecutor in Vermont cited connections between the defendant, Teresa Youngblut, and people linked to other murder investigations.

The gun used in the shooting death of a Delaware County couple was used in connection with the line-of-duty shooting death of a border patrol agent in Vermont, officials said.

The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives sent an alert to federally licensed firearms dealers a day after the shooting seeking information related to any gun purchases by Michelle Jacqueline Zajko.

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

A federal judge agreed Thursday to the prosecution’s request that Teresa Youngblut be detained while her case proceeds because the evidence appeared “to be strong.”