The Long Island rich kid on trial for attempted murder snapped selfies moments after nearly bludgeoning his cousin’s ex to death with a sledgehammer, a witness testified Friday.

Jacob Nolan, 23, took the creepy photos of himself on Nov. 12, 2012, as he sat in the hallway of victim Michael Weiss’ West 57th Street home office — his white shirt drenched in blood — just as cops rushed in.

“At the time, it seemed that he was taking pictures of himself,” building manager Andrew Goldfarb told jurors.

Lawyers for Nolan claim his older, “manipulative” cousin Pamela Buchbinder — the mother of Weiss’ young son — put him up to the grisly attack so she could cash in on his $1.5 million insurance policy.

Buchbinder hasn’t been charged.

As Nolan took pics, Weiss lay nearby. The victim survived.