A coked-up “delusional conspiracy theorist” in Florida beat his father to death in a rage over the parent receiving a vaccine, according to charging documents.

Brian McGann Jr., 44, is believed to have killed his father, Brian McGann Sr., during a rambling, 20-minute phone call with a female family friend that started shortly after 11 p.m. Sunday, records viewed by The Post revealed.

During the frantic exchange, the family friend allegedly heard McGann Sr. cry out, “Stop, you’re killing me” during an argument at his Lake Worth Beach home, the document noted.

The individual also claimed to have heard McGann Jr. screaming at and attacking his father before muttering, “He is under my foot.”

The family friend called 911 and told investigators that the younger McGann was a “delusional conspiracy theorist” who became enraged “because he recently learned his father received the vaccine,” the complaint stated.

McGann Jr. had also recently started using cocaine, the family friend told authorities.

When authorities arrived, they found McGann Sr. with his “clothing completely covered in blood” and his face seriously injured, the report stated.

He was pronounced dead by paramedics around 12:15 a.m.

Authorities observed McGann Jr. jumping over the back gate into a nearby backyard, only to track him down a few moments later and find him “completely covered in blood.”

Both his hands were also swollen and he had a cut on his left hand, in addition to lacerations on his fingers, the investigators noted.

McGann Jr. was arrested and charged with first-degree murder.

McGann Jr. was booked into Palm Beach County Jail, where he is being held without bond, according to CBS12.

He looked dejected during his Tuesday court appearance, WPBF reported.

McGann Jr. is being represented by a public defender who is not commenting on the case.

The Palm Beach County Sheriff’s Office declined to comment when contacted by The Post.