Every year, Maria Lazaro-Castillo planned a Halloween-themed birthday party for her 12-year-old daughter.But this year, just days before the celebration, Lazaro-Castillo, 41, was fatally shot while sitting in her car Sunday morning in McKinley Park, and a manhunt is underway for the person police say is responsible: her ex-boyfriend.“[Her kids] meant the world,” Miguel Valenzuela, Lazaro-Castillo’s brother-in-law told the Sun-Times. “She’ll make it to their events, field trips, graduations. … She made sure she was there.”Lazaro-Castillo was sitting in a 2013 Nissan Pathfinder with her 48-year-old ex-boyfriend around 9:20 a.m. Sunday in the 3800 block of South Damen Avenue when he left the passenger side of the vehicle and shot her multiple times in her head and chest after a brief dispute, according to police reports obtained by the Chicago Sun-Times.A witness told police he heard Lazaro-Castillo and her ex-boyfriend arguing and heard the man say something to the effect of: “I can’t do this anymore” before firing at least three shots, according to the police reports.Lazaro-Castillo was taken to Stroger Hospital where she died of multiple gunshot wounds less than an hour later. The ex-boyfriend fled, "eluding police," but detectives made telephone contact with the man, "who is refusing to turn himself in and has told family members that he will be taking his own life," according to the reports.Since then, detectives have continued to try to find him, but as of midday Thursday they had not.According to a message broadcast on police radio, he is "armed and dangerous." The alert, which included his name, said he was most recently seen in a white Chrysler Town & County with Illinois license plates IT9950D.Valenzuela described agonizing moments shortly after the attack when one of Lazaro-Castillo’s daughters called him when she didn’t pick them up from church. Her mom's location was pinging via a tracking app, so Valenzuela headed that way only to find red and yellow crime scene tape around her SUV.“As we were driving to the place, we [were thinking] just anything positive. [She’s] asleep, her phone died, or she was eating. Anything other than the worst,” Valenzuela, 37, said. “The heartbreak to see her vehicle with tape all around it and police officers, you’re at a loss for words.”Lazaro-Castillo had received an order of protection against the ex-boyfriend this month, but it hadn't been served to him at the time of the shooting, according to the reports and Valenzuela. Last year, domestic violence deaths spiked 110% in Illinois, and Valenzuela urged those suffering from domestic abuse to speak out about what they’re going through.“[Lazaro-Castillo] felt she was probably alone and couldn’t talk to anybody about this,” Valenzuela said. “No matter what, no matter who, speak out because life is short and tomorrow isn’t guaranteed.”“Karina’s Bill,” which aims to better protecting victims, focuses on taking guns from those accused of domestic violence and would require law enforcement to remove firearms when serving an emergency order of protection. The legislation, which has been stalled in Springfield for more than a year, was named after Karina Gonzalez, who was fatally shot, along with her 15-year-old daughter, at their Little Village home, allegedly by Gonzalez’s husband who had been ordered to stay away from them.Lazaro-Castillo was a “jack of all trades” who worked at Whole Foods but also had a passion for designing shirts and mugs in her spare time.Her smile was the first thing anyone noticed about her, and she had “powerful eyes that ran in the family,” according to Valenzuela.Lazaro-Castillo had a 9-year-old son and two daughters — 18 and 12 — who she “put first over anything and everything,” Valenzuela said. They often spent Christmas and birthdays donating to the homeless.Valenzuela created a GoFundMe fundraiser to help support her family. The page has raised more than $7,500 as of Thursday morning.“We’re still hoping we can wake up from this dream and it’s not true,” Valenzuela added.Contributing: Sophie Sherry