CENTRAL ISLIP, N.Y. — In September, at the Long Island cul-de-sac where two years ago her teenage daughter was found murdered by the transnational gang MS-13, Evelyn Rodriguez saw that the memorial she had placed there that day was gone.

The woman who had dismantled it — because she was trying to sell the house behind it — was about to drive off with the destroyed mementos, the authorities would later learn.

Ms. Rodriguez, who had become a nationally-known anti-gang activist following the killing of her daughter, Kayla Cuevas, confronted the driver, as did Kayla’s father. In the ensuing horrific scene caught on video by a local news crew and confirmed by the Suffolk County prosecutor’s office, the driver, Annmarie Drago, first hit Ms. Rodriguez with her front wheel, causing Ms. Rodriguez to flip onto the pavement.

Ms. Drago then kept going, running over her body with the back tire, fatally crushing Ms. Rodriguez.