ABC NewsBY: JON HAWORTH, AARON KATERSKY, MARK CRUDELE, and IVAN PEREIRA

(NEW YORK) —  Roy Den Hollander, whom the FBI has called the “primary subject” in the shooting at Judge Esther Salas’ New Jersey home, was also the leading suspect in the murder of a like-minded attorney in California earlier this month, the FBI said.

Hollander, an attorney who took on cases against feminist causes, was found dead by police Monday from an apparent suicide, according to investigators.

Hollander allegedly posed as a FedEx employee when he approached Salas’ home Sunday evening and shot Salas’ husband, Mark Anderl, and her son, Daniel Anderl, 20, before escaping in a car, according to sources. Daniel Anderl was killed and Mark Anderl is recovering at Robert Wood Johnson Hospital in New Brunswick, New Jersey.

Law enforcement sources say the suspect who killed men’s rights attorney Marc Angelucci on July 11 in San Bernardino County dressed in a similar disguise. The FBI’s Newark office said in a statement on Wednesday it is working with its San Bernardino counterpart and has evidence linking the Angelucci’s murder to Hollander.

While the FBI didn’t provide more details, law enforcement sources told ABC News the gun used in the California incident was the same one used in the New Jersey shootings.

Hollander had previously received media attention for lawsuits challenging perceived infringements of “men’s rights” on networks like Fox News, Comedy Central and MSNBC. Investigators are looking into whether Hollander was jealous of Angelucci for winning a recent case, according to law enforcement sources.

In the meantime, investigators in New York and New Jersey are taking precautions to protect people who may have been Hollander’s alleged targets.

During conference call with reporters, New York Gov. Andrew Cuomo said he ordered state police to provide protection for New York State Chief Judge Janet DiFiore, who may have been targeted by Hollander.

A municipal employee discovered Hollander’s body in a car in the town of Rockland, New York, according to the New York State Police. He died of an apparent self-inflicted gunshot wound, police said.

Inside Hollander’s vehicle was a photo of Judge DiFiore along with her address, according to Cuomo. Sources told ABC News that a dozen other names were found in Hollander’s car.

Shortly after the shooting Sunday night, security was ramped up for all federal judges in New Jersey, a law enforcement official told ABC News. Officials feared the incident at Judge Salas’ home could be the beginning of a coordinated attack.

“Our hearts, thoughts, prayers, are overwhelming with Judge Salas and her husband and hope that he makes a speedy recovery,” New Jersey Gov. Phil Murphy said on Wednesday. “This notion we made a lot of progress on gun safety … there are too many examples that continue to tell us that we are not home yet, we have a ways to go.”

Hollander, 72, had been diagnosed with cancer and officials are investigating whether the attacks were grudge killings committed by someone who knew they were dying, according to sources.

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