GREENVILLE, Texas (AP) -- Authorities are investigating the death of a rare white buffalo on a North Texas ranch just days shy of its first birthday.

Lakota Ranch owner Arby Little Soldier says he found the buffalo, named Lightning Medicine Cloud, dead Monday. The buffalo's mother was found dead the next day.

Last year, thousands attended a naming ceremony to celebrate the calf's May 12 birth.

According to Lakota Sioux lore, the goddess of peace once appeared in the form of a white buffalo calf.

Arby Little Soldier says the calf "was the hope of all nations." He said a birthday celebration planned this month will be a memorial instead.

Hunt County Sheriff Randy Meeks said his agency is working with the Texas Rangers to determine "whom or what killed Lighting Medicine Cloud."

Copyright 2012 The AP.