Fallen officer Charles Knox was honored with a plaque near where he was killed in 1992. The plaque appears to have been removed, police say.

Dunn was also an active captain in the Army National Guard. On Wednesday, he will be laid to rest. FOX31's Greg Nieto spoke to some of those organizing the memorial events on Wednesday.

PHILADELPHIA (WPVI) -- A plaque dedicated to a fallen Philadelphia police officer has gone missing, and now investigators are trying to figure out what happened to it. The plaque was placed in memory of Ofc. Charles Knox, who was killed in the line of duty during the summer of 1992.