Bullets wrapped in “wet” underwear were found in Luigi Mangione’s backpack following his arrest, a Pennsylvania cop testified Monday — as Manhattan prosecutors unveiled notes apparently written by the accused assassin, including one that said “pluck eyebrows.”

Officer Christy Wasser, of the Altoona Police Department, described finding the damp, gray Hanes underwear in Mangione’s bag after he was busted at a local McDonald’s, testifying that “when I opened it up, it was a magazine,” which was fully loaded.

As cops pulled the bullets out of the bag, one officer could be heard saying, “Damn dude, it’s f–king him – 100%,” according to bodycam footage played in Manhattan Supreme Court.

Wasser testified about the bizarre discovery during the ongoing, marathon evidence suppression hearing in the sensational case, in which Mangione, 27, is accused of gunning down UnitedHealthcare CEO Brian Thompson on a Midtown street last year.

Authorities also found several notes in Mangione’s belongings during a second search at the Altoona police station when he was taken into custody in the Pennsylvania city on Dec. 9, 2024, five days after Thompson’s execution.

One missive seemed to include a reminder for Mangione to “pluck eyebrows,” and also listed several Ohio cities, such as Columbus, Cleveland and Cincinnati, said Manhattan Assistant District Attorney Joel Seidemann.

Photos later released by prosecutors also showed the contents of Mangione’s backpack, which included a pair of tweezers to complete the brow grooming task.

Another piece of paper was a hand-drawn map of Pittsburgh — located about 100 miles west of Altoona — including possible escape routes, according to Manhattan prosecutors. A third, “to do” list style note listed “Check Pittsburg redeyes,” noting to “keep momentum, FBI slower overnight.”

The gun allegedly used to execute Thompson, a silencer and a red notebook that contained Mangione’s apparent manifesto were also found at the police station, according to testimony.

A photo of the red notebook was shared in court on Monday, the fourth day of the pre-trial hearing.

The defense has pushed for a judge to bar some damning evidence, including the alleged murder weapon, from Mangione’s trial, arguing Altoona cops didn’t have a warrant when they found the items. 

Prosecutors have countered that all the evidence collection was done by the book.

Wasser, a 19-year veteran of the department, said she wanted to check Mangione’s bag for bombs after he was placed under arrest because she didn’t want to pull a Moser,” in reference to a former officer who once inadvertently brought a bomb back to the police station.  

Pressed by Mangione’s attorney Karen Friedman Agnifilo, Wasser insisted she always searches the bags of a suspect who’s just been arrested, and didn’t single out Mangione because he was the alleged wanted CEO shooter.

Authorities ended up placing some of the evidence, like a hoagie and laptop inside a McDonald’s bag before leaving the chain restaurant and going to the station, according to testimony. 

Photos released by the district attorney’s office over the weekend showed a checklist Mangione also had in his belongings that included a trip to Best Buy and items like a USB 256 flash drive, a digital camera and a light source next to the store’s name and under a Dec. 8 date.

“Hot meal + water bottles” and trash bags were also scribbled in, according to the photo.

“Intel check in” next to Dec. 9 and “survival kit” were written down under “Future TO DO.”

On top of seeking to prohibit the items from being brought up at trial, Mangione’s defense team is also fighting to bar several statements he made to authorities following his arrest.

Before the hearing resumed Monday, the accused cold-blooded killer flashed a fist pump as he looked directly into the camera and listened to his attorney Friedman Agnifilo at the defense table in the courtroom.

More photos released by prosecutors showed Mangione also had a small flashlight, a USB drive attached to a silver necklace, a pocket knife and thousands of dollars in $100 bills on him when Altoona authorities hauled him into custody.

He also had a bus ticket with the name “Sam Dawson” on it that was supposed to travel from Philadelphia to Pittsburgh on Dec. 4, 2024 — the same day the Ivy League school grad allegedly gunned down Thompson. 

It was not clear if Mangione bought the ticket himself. Sam Dawson is the name of the intellectually disabled titular character played by Sean Penn in the 2001 film “I Am Sam.”

Court resumed this week after Mangione was too sick with an unspecified illness to make a court appearance on Friday.

Mangione, who also had a federal case hanging over his head, has pleaded not guilty to all charges. 

The hearing is set to continue Tuesday.

— Additional reporting by Ella Morrison