Seth "Andrea" Gregori, 21, is charged with two misdemeanors after allegedly planning an attack on police similar to the 2016 Dallas ambush.

Local and federal authorities are saying they thwarted a mass casualty attack Monday morning with the arrest of a 21-year-old Texas man accused of making terrorist threats against police officers.

A South Texas resident was arrested Monday after authorities say the 21-year-old threatened local police and was plotting an attack reminiscent of the deadly 2016 Dallas police ambush, officials said.

A Texas measles outbreak has doubled in the last week to 124 cases, state health officials said Tuesday, a day after they warned a person infected with the highly contagious disease had traveled from the outbreak zone.

The measles outbreak in Texas has escalated sharply to over 100 cases as health officials worry about the spread in other states.

Four of the newly reported cases are located in Dallam County, 200 miles north of Gaines County where the outbreak originated.