The latest message was found at Godwin High School on Friday, Oct. 2, when a student spotted a drawing of a gun, a date and a threat.
That student alerted his teacher.
On Sept. 30 and again on Oct. 1, two messages were discovered at Hungary Creek Middle School.
Lt. Chris Eley with Henrico County Police said the only similarity in what was found at the two schools is "in each case, someone wrote threatening messages in a restroom at the schools."
Police describe each incident as vandalism with a threatening nature.
Principals at both schools sent emails to parents to explain the situation.
Andy Jenks with Henrico County Public Schools said that in all three cases, students did exactly what they were supposed to do.
"We've got students who have done absolutely the right thing, which is to say, they saw something and they told and adult," Jenks said.
Police ask if parents or students have any information about the three incidents to contact law enforcement at Crime Solvers, at 780-1000.
Extra police will be staffed in and around the school buildings.