Brown U. janitor says he warned campus security about suspicious gunman twice in weeks leading up to mass shooting

A Brown University custodian spotted depraved gunman Claudio Neves Valente pacing school hallways and peering into classrooms nearly dozen times in the weeks before his mass shooting —  and  alerted campus security twice about the suspicious figure, a new report said.

Derek Lisi, who has worked at the elite school for 15 years, told the Boston Globe he “knew something was off with” the mass shooter before the sicko opened fire in a lecture hall, killing two  students, Dec. 13.

While Lisi said he twice told the same security guard about a suspicious person lurking around the same building in the days leading up to the horror, it’s unclear if any action was taken by the guard or  campus officials.

“He’d been casing that place for weeks,’’ looking into classrooms and “circling the hallways,’’ Lisi told the outlet of Neves Valente.

“I thought it was someone trying to steal something. Every time he saw me, I think he thought I was security, because he would always walk away.’’

“I said, ‘Something’s off with this guy, so I gotta say something,’ ” Lisi said.

Neither the school nor the private security firm believed to have employed the guard responded to the outlet’s request for comment.

Neves Valente, a former Brown grad student in the early 2000s, shot up the campus building  before gunning down MIT professor Nunu Loureiro at his home about 50 miles away  two days later.

The crazed shooter was found dead by suicide on Thursday night.

His motive is unclear, but former friends and classmates have said he looked down on Brown over everything from its food to supposed lack of academic intensity and had gone head to head in school with Loureiro as a younger man, earning better grades but ultimately going nowhere professionally while the dead man soared.

Brown officials did not immediately return an email seeking comment Monday afternoon.