LYNN – The Essex District Attorney’s police-involved shooting investigation into the death of a Boston man is underway, with shaken Jefferson Street residents vowing to make their neighborhood safer.”It scares me. I’m a mom,” said Katherine Guy.The midday incident turned hilly Jefferson Street, where Guy and her young daughters live with her grandparents, into a crime scene with three wrecked motor vehicles, two men under arrest and another – identified by the DA’s office as Rafael Suazo, 23, of Boston – in extremely serious condition.Suazo died Monday evening in Massachusetts General Hospital, said Carrie Kimball-Monahan, spokeswoman for District Attorney Jonathan Blodgett.According to Blodgett’s and Police Chief Kevin Coppinger’s accounts in published reports, two undercover police officers observed what they believed to be a drug transaction on Rock Avenue at 11:30 a.m. Monday.One officer arrested two alleged drug buyers. The other officer followed the suspected drug dealer, who drove to Jefferson Street. Once on Jefferson Street, the officer called for assistance, exited his vehicle and showed the suspect his badge.The suspect drove toward the officer, according to accounts, who fired a single shot at the driver. The suspect’s vehicle knocked the officer to the ground and the SUV continued down Jefferson Street, striking another moving vehicle.The crash occurred near the home where Guy lives with her 2-year-old and 5-year-old daughters and grandparents.”I heard a couple of bangs and a crash,” Guy said, adding she said she saw the injured officer run down Jefferson Street. “I tried to ask him if he was OK,” she said.The officer, who police and the DA have not identified, was taken to Salem Hospital where he was treated for his injuries and released. Published reports quoted Coppinger describing the officer as an 18-year department veteran with an exemplary record. Kimball-Monahan said investigators will interview witnesses, study ballistics and Medical Examiner’s reports and motor vehicle evidence.”We will gather the evidence to understand exactly what happened to determine if the officer was acting lawfully when he discharged his firearm,” Kimball-Monahan said.Sharona Landy, 32, and Vinchenzo Pintone, 33 – two Peabody residents identified by the DA’s office as allegedly purchasing heroin from Suazo – are scheduled to be arraigned today in Lynn District Court.Guy said her daughters were in her grandparents’ living room when the shooting and crash occurred. The incident left her worried about her family’s safety and committed to help returning Jefferson to its mostly quiet state.”We need to watch more for who is coming in and out of the city,” Guy said.