CALLAHAN, Fla. -

Nassau County deputies have arrested the father of a 9-month-old baby who drowned in a bathtub last week.

Robert Jerrell, 33, was arrested Monday and charged with manslaughter in the death of his son, Aaron (pictured below).

Investigators said Jerrell had taken a 2-year-old from the tub but left his baby alone in the bath at their home on Marlee Road in Callahan while he helped find a gasoline can for a relative. When he returned, the baby was unconscious in the water.

"I went through so many emotions, grief, anger, questions," said the boy's grandmother, who did not want to be identified. "I'm just completely distraught."

"He would have died for them. Those were his babies and he loved them," she said of the children's father.

Neighbor and mother Christa Vandigo said she can't believe how the boy died.

"That's really crazy," she said. "Most parents should know by now you can't leave a child alone in the bathtub."

The baby's grandmother said it was an honest mistake.

"It's a misunderstanding between the two brothers because one brother thought the other had got the other out," she said.

But Vandigo has a baby just one month younger than Aaron was and agrees with the manslaughter charge. Misunderstanding or not, she said the baby should never have been left alone in the first place.

"I think he should definitely get it," Vandigo said. "I mean, that's just stupid. You can never just leave your child in the bathtub, especially walking away, but to take a nap and just forget your 9-month-old? You just can't."

The Florida Department of Children and Families is also investigating the death.