The 29-year-olds each put a 22-caliber pistol to her head and pulled the triggers simultaneously at the Family Shooting Center at Cherry Creek State Park Monday afternoon.

One sister fell dead, and Thursday morning the other had recovered enough to tell investigators what happened.

But she would not say why during the emotional two-hour interview.

"We asked that question several times, and each time she declined to answer," said Capt. Louie Perea, of the Arapahoe County Sheriff's Department. "Obviously we can't make her tell us that."

He characterized her as "devastated, frustrated, distraught, angry at times."

Her parents are scheduled to arrive in Colorado Friday.