CUTLER BAY, Fla. -

The father of a man who police say left two children home alone before a fire started there called it a regrettable accident.

"It was just an accident," said Andrew Sepulveda's father.

According to an arrest affidavit, Andrew Sepulveda left the two children -- a 6-year-old girl and 4-year-old boy -- alone at the home and locked the doors, which prevented them from exiting when a fire started in the children's bedroom Wednesday. Sepulveda, 31, went to pick up groceries with his girlfriend and their own children and left the other two children at the home.

"That's completely out of character due to the fact that we know he tried his very best," said Sepulveda's father. "To me, it was a bad decision. That's the only thing I can tell you. Maybe he forgot but come on -- I'm not in his head. I haven't even spoken with him yet."

Sepulveda was supposed to be babysitting the children injured in the fire while their mother was at work. The two families were living in the same house for nearly two months.

Odney Johnson, who owns the one-story, single-family home in Cutler Bay, said he had been renting the home to Sepulveda, his girlfriend, their two children. He added he was unaware of the temporary living situation involved the other family.

Sepulveda's father said his son regularly cared for the women's two children, who attended school with his.

"He acts like that they're his kids and everything," he said.

Sepulveda is charged with two counts of child neglect with great bodily harm. He remained in jail Friday on $25,000 bond.

The two children remain at Jackson Memorial Hospital in serious condition.

"I hope it was just a mistake and pray to God everything came out today and we can make things better," said Sepulveda's father.