BOSTON -- A birthday celebration took a tragic turn during the weekend when an 18-year-old pregnant woman was shot and killed just after blowing out the candles on her cake.

Family and family gathered outside Paola Castillo's home at a makeshift memorial for the woman who died at her own birthday party.

"My sister was a wonderful person with a great heart," said the victim's sister, Keila Castillo.

"She was happy girl -- having a baby soon," one friend said.

It was a double celebration for Castillo, who just Friday learned she was having a boy. The party was at the apartment of one of Castillo's girlfriends in Hyde Park

Investigators believe the shooter was with a group of people who were asked to leave the party. After they left, the group fired several shots into the second-floor apartment.

"What I heard was a round of gunshots," another friend said. "She was arguing with somebody and they just shot her."

Police believe Castillo was targeted and officials said they are following several promising leads.

"Any problem we have she would always be there. Everybody loved her," another friend said.