Federal investigators are examining whether a suspect in the ambush shooting of a federal judge’s family in New Jersey also killed a fellow men’s rights lawyer in California, a law enforcement official said.

The federal agents are trying to determine whether Roy Den Hollander, who was found dead of a self-inflicted gunshot wound the day after an attack that killed the judge’s son and wounded her husband, had any role in the killing earlier this month of Marc Angelucci.

Angelucci, like Den Hollander, was involved in lawsuits alleging gender discrimination against men. He was shot to death July 11 at his home in San Bernardino County, California.

The official cautioned the investigation was in its early stages and federal officials were working with local homicide detectives. In both cases, the suspect appeared to pose as a delivery driver, the official said.

Investigators are also examining Den Hollander’s financial and travel records, as well as misogynistic screeds he posted online, said the official, who could not discuss an ongoing investigation publicly and spoke to the AP on condition of anonymity.

The San Bernardino County sheriff’s department referred questions to the FBI.

Den Hollander, 72, described himself as an “anti-feminist” attorney who filed lawsuits challenging the constitutionality of “ladies night” promotions at bars and nightclubs, sued Columbia University for providing women’s studies classes, and sued news organizations over what he said was biased coverage.

The FBI said Den Hollander was the “primary subject in the attack” Sunday at the home of U.S. District Judge Esther Salas in North Brunswick, New Jersey, where 20-year-old Daniel Anderl was killed and his father, Mark Anderl, 63, was wounded. Mark Anderl remained hospitalized and was expected to have more surgery Tuesday, according to Mayor Francis “Mac” Womack, a family friend.

Salas, 51, was in another part of the house and was unharmed.

Den Hollander was found dead Monday in Sullivan County, New York.

Investigators found items in his possession that raised concerns about whether he had targeted, or planned to target, other people, including a photograph of New York Chief Judge Janet DiFiore and the address of a state appeals courthouse, a state court spokesperson said.

Both Den Hollander and Angelucci, 52, were involved in lawsuits seeking to force the U.S. government to require all young women to join men in registering for a possible military draft.

Den Hollander’s lawsuit, filed in 2015 on behalf of a woman in New Jersey, was assigned to Salas. He withdrew as the lawyer in the case a year ago after being diagnosed with cancer.

Harry Crouch, president of the National Coalition for Men, told The Associated Press that Den Hollander was furious that he hadn’t been involved in a similar case being handled by Angelucci.

“Roy was just not happy that we did not involve him as a co-counsel. I think unhappy is an understatement,” Crouch said. “He called me up and threatened me.”

Crouch said Den Hollander did not have a good reputation among other men’s rights advocates.

“I think he was very hostile, very, very hostile that he finally went over the hill,” Crouch said.

In more than 2,000 pages of often misogynistic, racist writings posted online, Den Hollander had sharply criticized Salas and other female judges.

He also wrote about wanting to use the rest of his time on earth to “even the score” with his perceived enemies, using “cowboy justice.”

J. Steven Svoboda, a spokesman for the National Coalition for Men who said he was speaking personally and not on behalf of the organization, said Angelucci was “beloved” for his “groundbreaking legal work all. in his mind, to make the world a better place.”