The phrase "chalk outline" refers to a drawing made with chalk or similar material on the ground to trace the shape of a body, usually at a crime scene. It is commonly used to symbolize death or the aftermath of a violent incident. Full definition
Johnny would then draw by freehand using chalk the outline of an animal such as a zebra. (safarivet.com)
With broken mirrors scattered over the figure like bruises or bullet wounds, the figures look like chalk outlines of corpses at crime scenes. (artfcity.com)
The Naked Gun movies have always relied heavily on slapstick humor — prepare to see Barbara Bush get smacked down, hard and often — and visual gags (one of my favorite scenes is after an explosion where the filmmakers had a blast — hah — planting funny chalk outlines all over the place). (mutantreviewers.wordpress.com)