Sheriff Larry Fowler says 17-year-old Jake Evans reloaded the .22 revolver at least once during the shootings. When Evans called 911 at 12:34 a.m. Thursday to report the deaths, his voice was "calm."
Responding deputies found the body of Evans' 15-year-old sister first, then the mother, 48-year-old Jami Evans. The shootings happened in the family's upscale home off River Creek Lane in Aledo.
Evans' father, Darryl Evans, was out of town on business at the time.
Fowler said Jake Evans was enrolled in Aledo High School until this past January, when he abruptly withdrew and began home-schooling. Fowler did not provide a reason why he left school, or a motive for the killings.
Victim Jami Evans was a former first-grade teacher and assistant principal at two Aledo ISD schools. She was already homeschooling her younger daughter since January 2010. District superintendent Dan Manning says counseling will be provided at all schools.
Evans allegedly obtained the gun from his grandfather, a retired Fort Worth police officer who lives nearby.
According to a news release, Evans was arrested without incident at the house. He will be charged with capital murder.
There are two older sisters in the Evans family, but they were not home during the shootings, Fowler said.
FOX 4 has obtained a copy of the 911 call. Watch for more updates on FOX 4 News starting at 5 p.m., and on myfoxdfw.com.
Sheriff: Parker County teen killed mother, sisterMore>>