A memorial plaque dedicated to a fallen Philadelphia police officer has gone missing, police announced. Now, an investigation is underway into what happened to it. According to police, the plaque — which is dedicated to Officer Charles Knox, who was killed in the line of duty in 1992 — was reported missing around 8 p.m. on Tuesday, Nov. 12. Police said an officer was on routine patrol and noticed the plaque was removed from its original spot on the sidewalk on the 2000 block of S. Broad St. The Fraternal Order of Police and management at the nearby Walgreens store confirmed that no permission was granted for the plaque’s removal, police said. Police said photographs of the site showed a significant amount of dirt and debris, suggesting the plaque may have been missing for an extended period. According to police, investigators are reviewing footage from area Real-Time Crime Center cameras to determine if any evidence can be found regarding the plaque’s disappearance. “The Philadelphia Police Department is committed to preserving the memory of our fallen officers,” Police Commissioner Kevin J. Bethel said in a news release. “We are taking this matter very seriously and are asking anyone with information to please come forward.” The plaque — which was set in the ground — reads, “In memory of Police Officer Charles T. Knox. Died in the line of duty protecting the citizens of Philadelphia on August 30, 1992. Dedicated by his Family and Friends.” Police said Knox had been fatally shot while responding to an armed robbery at a Roy Roger’s restaurant located at 1401 Snyder Ave. Upon entering the establishment, police said Knox encountered a suspect holding a firearm to the head of the manager. He commanded the suspect to drop the weapon, but the individual instead lunged at him. A second suspect emerged from the manager’s office behind Knox during the struggle, according to police. The individual placed a handgun beneath Knox’s vest and fired a shot that caused him to fall to the ground. While Knox lay face-up, the suspect fired again, striking him in the cheek and taking his life, police said. Both suspects were later captured and received life sentences for their roles in the murder. Knox had spent two years with the Philadelphia Police Department. Anyone with information about the missing plaque is urged to contact South Detectives Division at 215-686-3013 or call 215-686-TIPS (8477). Sign up for our Breaking newsletter to get the most urgent news stories in your inbox.