(CNN) -- A 12-year-old west Florida boy apparently struck by a bullet fired skyward during a New Year's Eve celebration is improving, but remains in serious condition, authorities said Tuesday.
Overnight, his condition was upgraded from critical to serious, said Larry McKinnon of the Hillsborough County Sheriff's Office.
The bullet is still lodged in the boy's head, and doctors are working to control the swelling around his brain. Until the bullet is removed, detectives cannot compare it to other bullets to help determine a possible suspect in the shooting, said McKinnon.
Diego Duran, 12, was sitting in the front yard of his Ruskin, Florida, home watching fireworks about 1 a.m. Sunday when he fell to the ground, bleeding from the nose and eyes, McKinnon said.
The victim's mother drove him to South Bay Hospital in Sun City Center, where doctors determined that a gunshot had gone through the top of the boy's head. The child was then transported to Tampa General Hospital, where he was in critical condition Sunday afternoon.
The boy's mother, Sandy Duran, spoke to reporters Monday about her son.
"His brain is still in that stage of the 48 to 72 hours where it swells. There's a lot of inflammation going on, so the doctors cannot say what he will and won't be able to do," she said. "The good news is that he is moving his extremities. He can move his hands. He can move his legs. He has opened his eyes."
Duran described her son as "noble" and said he enjoyed skating and playing guitar. He is the youngest of three children, and her family is taking it "hour by hour," she said.
"For me, it's a miracle that he's alive considering what has just happened to him," said Duran.
No one in the immediate area around the victim's house was firing a gun, the boy's relatives and neighbors told detectives. Police believe that celebratory gunfire, possibly shot from miles away, wounded the boy.
If the wound is determined to be from a celebratory gunshot, it would not be the first time a child was inadvertently shot in the Southeast on New Year's Eve and in the hours after midnight. In 2009, 4-year-old Marquel Peters died after a bullet went through the roof of a suburban Atlanta church and hit him.
The boy's mother, Nathalee Peters, has launched an online effort -- called Marquel's Pledge -- to urge people not to shoot into the air in celebration. It's one of several such campaigns nationwide, including one in Miami called, "One bullet kills the party."
Duran similarly spoke about the need to educate the public about the dangers of celebratory gunfire.
"I'm speaking out because I don't think there's enough awareness out there," she said. "A firearm is a weapon. It's a weapon that takes a life. It's not a toy for celebration."
CNN's George Howell contributed to this report.