CUTLER BAY, Fla. -

A babysitter has been arrested after he left two children, ages 4 and 6, alone before a fire started at their home in Cutler Bay, Miami-Dade police say.

The house fire happened at 10241 Martinique Drive about 1:30 p.m. Wednesday.

The children, both in cardiac arrest, were airlifted to the Trauma Center at Jackson Memorial Hospital, in serious condition, authorities say. Both suffered smoke inhalation.

Andrew Richard Sepulveda, 31, is facing two counts of child neglect with great bodily harm.

Sepulveda left the home before the fire with his two children and their mother, leaving the other two kids home alone, police say.

"I saw the smoke coming out of the house," said one witness.

Miami-Dade police detective Roy Rutland said Sepulveda went to pick up groceries.

"I don't think you need to be a detective to look at this scene behind me to realize we have two small children left alone and realize that's a concern," said Rutland.

According to the affidavit, Sepulveda left the children alone at the home and locked the doors of the home, which prevented them from exiting.

Police believe the two children then somehow sparked the fire.

"They were hysterical," said another witness. "They were crying. The mom was pacing back and forth. The dad was on the phone with his hand on his head and they didn't know what to do."

It's unclear how the fire started. The investigation is ongoing.