The family of four was injured during a road rage incident on July 4.
Deputies said 18-year-old Bayron Rivera fired a gun at the family because he was upset the family's father cut him off on the road.
The family tells ABC News their 1-year-old underwent surgery Monday and is recovering.
The father and the 2-year-old, however, are still hospitalized.
They said the burns from the explosion left one of the children unrecognizable.
Deputies said the investigation showed Rivera used an AR-15 style rifle to fire into the family's car.
They said the family and Rivera did not know each other.
Rivera surrendered to deputies Sunday and is now being held on a $120,000 bond.
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"Our main concern has been to the two children that have been severely injured and face a very long long recovery," said Sheriff Ed Gonzalez in a press conference.
The lead lieutenant on the case said Rivera told them he did not know children were in the car at the time of the shooting.