10 Injured in Drive-By Shooting in Paramount : Violence: Gunfire shatters teen-ager’s birthday party, leaving her sister brain-dead. An 8-month-old is also wounded in the attack.

Wilnelia Bonilla was celebrating her 17th birthday Sunday morning when gunmen opened fire on the gathering, spraying more than two dozen bullets into the living room of the modest rental home in Paramount, authorities said.

Ten people were injured in the 12:45 a.m. attack, including an 8-month-old, and Wilnelia’s 21-year-old sister, Maritza, who was critically wounded and placed on life support systems. Family members said doctors had told them Maritza, who was engaged to be married in February, is “brain-dead.”

Wilnelia’s 22-year-old brother, Joseli, and her 46-year-old father, Elisio, were also wounded.

“Why would they do this? Why?” Wilnelia asked as a steady stream of friends and neighbors came to the house in the 16400 block of Indiana Avenue on Sunday afternoon to offer condolences. “I just don’t understand. They’ve killed a member of our family, and we don’t even know why.”

About 30 minutes before the shootings, three men not associated with the party began arguing on the sidewalk a few houses away.

Two men began beating the third, who fled past the Bonilla house, Wilnelia said. Party-goers said the man stopped briefly in front of the house before running toward another party less than a block away.

Half an hour later, a beige van and a car drove slowly past the Bonilla house. Gunmen inside both vehicles opened fire, Wilnelia said.

“I thought it was firecrackers at first, but then I saw the smoke and I saw the splintered wood and I saw my sister on the floor and I knew,” she said. “My boyfriend was standing at the front door when it started and there’s this bullet right there that could have hit him, could have killed him. . . . He yelled for everybody to get down, but some of the bullets just bounced off things and hit people anyway.”

One bullet struck Maritza Bonilla just behind her right ear. Another struck Joseli Bonilla in the thigh; he was released from the hospital in good condition Sunday afternoon. Two more bullets hit their father, Elisio, in the legs and chest. He suffered a heart attack as he awaited surgery Sunday morning and was listed in serious condition at Harbor-UCLA Medical Center.

“He isn’t insured, and now he can’t work,” Wilnelia said. “I don’t know what we’re going to do.”

Also injured in the attack were 8-month-old Walter Gonzales, who was struck in the head and body. The baby was released from the hospital Sunday afternoon, but his mother, Patricia, remained hospitalized with bullet wounds in her arm and back. The baby’s father, Walter, suffered an arm injury.

Wilnelia said she suspects that the attackers shot at the Bonilla party by mistake.

“We have had so many parties, so many, and this is the first time anything bad has happened,” she said. “Maybe they thought we were somebody else.”

Los Angeles County sheriff’s Deputy Angie McLaughlin said investigators believe that the shooting is gang-related. None of the victims is a gang member.