Sister accidentally kills brother while posing for Facebook pictures

This is old news but its so sad, which is why i decided to post it again

A 19-year-old woman accidentally shot dead her brother while posing with a gun for Facebook photos on New Year's Eve.
Manuel Ortiz died instantly after being shot in the head at about 6am on Monday morning.
Family and friends wept as his body was carried from his apartment in Phoenix, Arizona, where the shooting took place.
Police said 22-year-old Ortiz and his sister Savannah Ramirez arrived back at the home they shared on New Year’s Eve after spending the night drinking.

I still don't understand why anyone will want to pose with a gun??