Evelyn Rodriguez, the mother of Kayla Cuevas, was fatally struck Friday, according to Rep. Peter King's office. The incident happened on Stahley Street near Ray Court just after 4 p.m.
Cuevas' body was discovered exactly two years ago and the memorial was being held to mark that occasion. Authorities say Rodriguez, 50, was struck before the memorial started -- possibly after getting into a dispute with a female driver over the placement of the memorial.
Police say the driver, who is the relative of a resident of Ray Court, was trying to drive away when she struck Rodriguez.
Rodriguez was transported to Southside Hospital in Bay Shore where she was pronounced dead.
The driver stayed at the scene and no charges were immediately filed, but Suffolk County Police Homicide Squad detectives are investigating.
King's office had been working closely with Rodriguez ever since the 2016 murder of her daughter and her daughter's friend. The murder of Cuevas, 16, and 15-year-old Nisa Mickens, shocked the community.
The girls are not believed to have been specifically targeted for retribution, but rather crimes of opportunity related to ongoing gang disputes at the high school.
The girls' alleged killers, who were arrested along with about a dozen other alleged MS-13 members, are facing murder charges that could result in the death penalty.
Rodriguez filed a $110 million lawsuit last December against the Brentwood School District, claiming it ignored warnings that MS-13 members were threatening Kayla.
Rodriguez said that employees failed to act when told that the girl was being threatened. The lawsuit says the bullying went on for two years before the teenager was killed.
She appealed to members of Congress in 2017 to take action to combat gang violence on Long Island, explaining her community was living in fear.
She also met with President Trump and attended the State of the Union address last January.
President Trump tweeted his condolences Friday night saying, 'My thoughts and prayers are with Evelyn Rodriguez this evening, along with her family and friends. #RIPEvelyn'
New York Gov. Andrew Cuomo said he has directed state police to provide any assistance and resources to Suffolk County police as they investigate Rodriguez's death.
"In the wake of the unspeakable tragedy of her daughter's death, Evelyn showed tremendous courage by dedicating herself to the disruption of gang violence throughout her community. As she stood by my side as we fought back against MS-13, I stand with her family tonight."
Suffolk County District Attorney Timothy Sini released the following statement:
"Evelyn Rodriguez endured unspeakable tragedy when her daughter was murdered two years ago. As a parent, I cannot imagine functioning after the loss of a child, but Evelyn was able to turn that tragedy into a mission for good. She harvested her grief and used it as a catalyst for positive change on behalf of her community and on behalf of this country. She was a fierce advocate for her hometown of Brentwood and was fearless in her fight to put an end to the violence caused by MS-13 to ensure that other parents never have to endure the pain she suffered. Evelyn is one of the strongest people I have ever met in my life. I am proud to have worked with her and even more proud to have called her a friend. I know I speak for everyone who knew Evelyn in saying that we are truly heartbroken over her loss."
Suffolk County police ask anyone with information on the incident to call the Homicide Squad at 631-852-6392.
The Associated Press contributed to this report.