News media set up in front of the home of U.S. District Judge Esther Salas on Monday in North Brunswick, N.J. A gunman posing as a delivery person shot and killed Salas’ 20-year-old son Sunday evening. The FBI says there could be a connection between this attack and one in California earlier this month.

Mark Lennihan/AP

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Mark Lennihan/AP

News media set up in front of the home of U.S. District Judge Esther Salas on Monday in North Brunswick, N.J. A gunman posing as a delivery person shot and killed Salas’ 20-year-old son Sunday evening. The FBI says there could be a connection between this attack and one in California earlier this month.

Mark Lennihan/AP

The alleged killer of the son of a New Jersey federal judge may also have been involved in the shooting death of a men’s rights attorney in California earlier this month, authorities said Wednesday.

Attorney Marc Angelucci was killed July 11 in San Bernardino County. Just over a week later, a man dressed as a FedEx driver showed up at the home of Judge Esther Salas, shot her son through the heart when he opened the door, and wounded Salas’s husband, who survived.

Authorities says they have evidence linking the alleged perpetrator in the New Jersey shooting, Roy Den Hollander, with Angelucci’s killing as well. A law enforcement official told the Associated Press that the suspect in Angelucci’s killings was also dressed as a delivery driver.

ABC News reports law enforcement sources said the same gun was used in both killings.

Hollander, 72, a self-proclaimed “anti-feminist” attorney, was known for filing lawsuits challenging the constitutionality of ladies’ nights at bars. He also sued Columbia University for offering women’s studies classes.

Angelucci, an attorney, was also a men’s rights activist. Like Hollander, Angelucci had filed cases challenging the male-only military draft. Angelucci’s friends say Hollander saw the California lawyer as a rival.

Hollander was “beyond words furious, absolutely enraged” that Angelucci was getting involved in the Selective Service case, his friend Paul Elam said in a Facebook live video Monday, CNN reports. “He saw Marc’s work in that respect as an intrusion into his space. He was more than angry about it; he was livid.”

Like Angelucci, Hollander had been a member of the National Coalition of Men, a men’s rights advocacy group. But Hollander was kicked out of the group after he threatened the group’s leadership, coalition president Harry Crouch told CNN.

Hollander was found dead Monday.