Pontiac Capt. Tim Atkins said her boyfriend was at the girl's side, trying to administer first aid.
The 17-year-old was rushed to McLaren Oakland Hospital
for treatment, and she
was later put on life support.
At the scene, deputies took the 18-year-old - who is believed to be the person who fired the gun - into custody.
A witness to the shooting was also taken to the sheriff's Pontiac substation for questioning.
The weapon used was found in a garbage can at the rear of the house, deputies said.
said preliminary investigations shows no evidence of an argument between the couple before the shooting.
However, detectives are still conducting interviews and following up on the incident, he