FRESNO (AP) — Police in Fresno are investigating a drive-by shooting that wounded a 6-year-old boy who was shot in the torso while sitting in the backseat of his mother’s car.

The Fresno Bee reports officers responded Monday to a call of shots fire near the Fresno airport and found more than 20 shell casings in the road, but no signs of a victim.

Fresno Police Lt. Charlie Chamalbide says a second call revealed that the boy’s mother had driven him to a hospital where he was admitted and is in critical but guarded condition.

He says the mother told investigators she was in the area picking up a second child when she heard what she thought were fireworks.

Chamalbide says police believe it could have been a gang-related shooting, but have no information on possible suspects or vehicles.