A fitness instructor has been slain at a North Texas church and investigators are seeking a man dressed as a police officer who was seen on security video.

Midlothian (mid-LOHTH'-ee-uhn) police say the body of 45-year-old Terri "Missy" Bevers (BEE'-vers) of Red Oak was found Monday by a student arriving for a class.

Bevers, who was a married mother of three, was killed at Creekside Church of Christ in Midlothian, 20 miles southwest of Dallas. No cause of death was immediately released.

Capt. John Spann says officers found broken glass on the floor and evidence of forced entry into the church, possibly for a burglary.

The video shows the man inside the church minutes before the victim arrived before dawn Monday. He wore a jacket labeled "Police," gloves and a helmet.