From The Guardian which has the disturbing video:
Police in Evansville, Indiana, arrested the the mother of a one-year-old baby and her boyfriend after they discovered a video of the child playing with a 40-caliber handgun, police said in a statement.
Police found the video on a cellphone owned by Michael Barnes, a 19-year-old robbery suspect who was arrested on Thursday night after selling a handgun to an undercover officer. Police said they searched Barnes’ phone after his arrest and found the video, which shows the child playing with the weapon. The boy is seen putting the muzzle in his mouth as Barnes instructs the child to say “pow”.
Police said they determined that Barnes’ girlfriend, Toni Wilson, 22, was present while Barnes filmed the boy playing with the gun. Police said that when they questioned the woman on Friday, she claimed the weapon shown in the video was a pellet gun.