Luigi Mangione's Mom Told Cops 'Might Be Something She Could See Him Doing'

Luigi Mangione's mother knew he was capable of extreme actions -- hinting at his current state of mind when questioned by police just days before his arrest for the murder of UnitedHealthcare CEO Brian Thompson.

Following Luigi's first-degree murder indictment Tuesday, NYPD Chief of Detectives Joseph Kenny revealed during a Manhattan D.A. press conference that, before his arrest, they called the suspect's mother, Kathleen Mangione, while vetting a tip from the San Francisco FBI office related to a missing-person case.

Kenny said Kathleen seemed unsurprised, saying, "They had a conversation where she didn’t indicate that it was her son in the photograph, but she said it might be something that she could see him doing."

Law enforcement sources tell TMZ ... Kathleen’s statement indicated she knew her son was angry at the healthcare industry and that he was capable of going to extreme lengths to carry out these crimes.

We're told it’s possible she knew about his writings or that he had verbally expressed issues with the healthcare industry. Bottom line: she knew her son.

Days earlier, it emerged that the FBI contacted Kathleen to update her after she reported Luigi missing last month ... telling her the suspect bore some resemblance to her son -- just the day before he was arrested for Thompson’s murder.

It was police in San Fran, where Luigi was reported missing, who tipped off the feds that the suspected shooter and the missing 26-year-old could be the same person.

Luigi was caught the next morning while eating at a McDonald's in Pennsylvania, after customers told an employee he looked like the guy from the nationwide manhunt.