ST. LOUIS COUNTY - The St. Louis County Prosecuting Attorney’s Office on Tuesday, Feb. 24, 2026, charged Jesse St. John, 28, with first-degree murder and armed criminal action in the death of 19-year-old Steffon Marmon, authorities said.
Get The Latest News!
Don't miss our top stories and need-to-know news everyday in your inbox.
St. John, of the 300 block of Henquin Drive in St. Louis, Mo., 63135, is being held on a $750,000 cash-only bond with no 10% option, according to the prosecutor’s office.
Police were called to a disturbance and, upon arriving, encountered the victim’s mother outside the house where the victim was staying, the probable cause statement said. Officers who went inside found the victim deceased with apparent bullet wounds to the back. Multiple .45 caliber shell casings were found at the scene, the statement said.
Detectives determined through investigation that St. John was in the area during the time of the murder based on his cell phone location data, the statement said. A witness also described and later identified St. John as the last person in the house alone with the victim before his death, according to the statement.
St. John was later arrested on an unrelated offense and a firearm was recovered, the statement said. Lab analysis confirmed the firearm matched the shell casings recovered at the scene, according to the statement. A records check showed St. John has a prior felony conviction for first-degree robbery and armed criminal action, the statement said.
Marmon was previously identified by authorities on Jan. 6 as a 19-year-old from the 2000 block of Switzer Avenue in St. Louis, Missouri 63136.
St. Louis County Police Department Crimes Against Persons detectives are handling the investigation.
Charges are merely an accusation, and defendants are presumed innocent unless and until proven guilty in a court of law.
