As federal authorities continue to investigate the murder of a federal judge’s son and shooting of her husband at their North Brunswick home, the gunman is being investigated as a possible suspect in another killing.

The FBI has identified the shooter as Roy Den Hollander, a self-described “anti-feminist” attorney. Investigators say that Den Hollander dressed up like a FedEx employee before he showed up at the home of Judge Esther Salas Sunday evening and opened fire inside the home. Salas’ son, Daniel Anderl, was killed and husband Mark Anderl was wounded.

Den Hollander was found dead just across the New York-New Jersey border the next day, reportedly from a self-inflicted gunshot wound.

Federal marshals were at the North Brunswick home Tuesday standing guard, and Judge Salas is said to be under constant security protection.

Den Hollander appeared before Salas in a 2019 case that attempted to require women to register for the military draft. Salas allowed that case to proceed.

Authorities say that the shooting at the house may have not been the only violence Den Hollander sought. A spokesperson for New York Chief Judge Janet DiFiore says the FBI found the judge’s picture in his car. DiFiore is now receiving 24-hour police protection, according to New York Gov. Andrew Cuomo.

Federal authorities are also trying to determine whether Den Hollander had any role in the killing of attorney Marc Angelucci in San Bernardino County, California, earlier this month. A person fitting Den Hollander’s description is considered to be involved in the killing.

But the FBI and San Bernardino sheriff’s department did not respond to requests for comment about the California case.