TAMPA — The bullet wasn't meant for 14-year-old Dinorah Rodriguez.

The boy who shot her, Dereck Polanco Rivera, 16, was targeting a different teenager when he fired into a vehicle carrying four people including Rodriguez during the early morning hours of June 17, according to the Hillsborough County Sheriff's Office.

He was after someone he had a "beef" with, the Sheriff's Office said. Instead, one of his shots hit Rodriguez in the head, fatally injuring her.

Rivera was arrested Tuesday night, a week later, on charges including second-degree murder.

The nature of the beef, and why it took gunfire to settle it, remained unknown Tuesday, the Sheriff's Office said.

A man who said he is Rivera's brother, Mathew Santiago, couldn't shed any light during an interview outside the home they share with their parents in the Woodridge at Carrollwood apartments near Dale Mabry Highway and Humphrey Street.

But Santiago, 18, questions who was the aggressor, and insists he knows one thing: "If they had all gone their separate ways, it wouldn't have happened."

Rivera was involved with a gang known as the "TC Boys," based out of Town 'n' Country, but the shooting is not considered gang-related, the Sheriff's Office said.

Family members have confirmed to the Times that the victim is Rodriguez, but they said they weren't ready to talk yet. The Sheriff's Office has declined to release her name because of its interpretation of a constitutional amendment known as Marsy's Law, designed to protect crime victims.

Deputies found Rodriguez about 1:40 a.m. June 17 inside a vehicle in the parking lot of a Walgreens drug store, 128 E Brandon Blvd. Suffering from a gunshot wound, she was flown to Tampa General Hospital. She died the next day.

After interviewing witnesses, deputies learned that the shooting took place at the intersection of Kingsway Road and Clay Avenue, about a mile from the Walgreens.

Rivera fired a number of shots as the vehicle approached the intersection, the Sheriff's Office said.

Three other people in the vehicle were not injured. The driver was a woman. The group had just left a house party on Rollingwood Lane in Valrico, the Sheriff's Office said.

"What this is, or what prompted him to resort to this type of violence, we're still not sure," Sheriff Chad Chronister said at a news conference Wednesday. "We're still working through that."

Rivera was transported to the county Juvenile Assessment Center and faces charges of second degree murder and throwing a deadly missile at, within or into a vehicle.

The Hillsborough State Attorney's Office will determine whether to charge Rivera as an adult. The decision could take several days as prosecutors review evidence in the case, said Estella Gray, a spokeswoman for the office.

Mathew Santiago said his brother had been pulled out of Leto High School by his family about three years ago, but he declined to elaborate.

Rivera was "just supposed to be having fun with the boys this summer," Santiago said.

He said neither he nor his brother knew Rodriguez and he questions the Sheriff's Office account of what happened.

"They happened to be there at the wrong time — everybody involved," he said.

Contact Sam Ogozalek at sogozalek@tampabay.com.