A 21-year-old woman riding her bicycle in Staten Island was killed when a boat, hitched to the back of a SUV, somehow detached from the vehicle and crushed her. Another bicyclist, a 22-year-old woman, was also injured, and police say it happened when the driver was trying to pass the cyclists.

Officers responded to the incident at 5:18 p.m., at Hylan Boulevard and Redgrace Avenue in the Great Kills section. The preliminary investigation says that the driver of a 2015 Toyota SUV was heading north on Hylan Boulevard with a boat in tow, when he "attempted to change lanes from the right lane to the center lane while proceeding to overtake two bicyclists in the right lane."

But when the SUV changed lanes, police say, "its trailer became detached and continued to travel north into the right lane, striking Bicyclist # 2, a 22 year-old female. The boat continued to travel north striking bicyclist # 1, a 21 year-old female who became pinned under the vehicle as it came to rest."

Both women were taken to Staten Island University Hospital, where the 21-year-old, identified as Alexa Cioffi, died. The other victim "suffered damage to her chest, pelvis and one of her arms, as well as head trauma," sources told the Staten Island Advance. She is currently in stable condition.

A witness told the Daily News, "They were both hit — thud, thud. One woman was under the boat. The other woman was lying facedown by the light pole.'

The investigation is ongoing and no charges have been filed. The SUV's driver stayed at the scene and was eventually released by investigators. As he left, WABC 7's reporter Jim Dolan tried to ask him what happened, saying, "The boat's not supposed to become detached—can you explain how that happened?" The driver departed without responding or offering condolences.

Dolan also said it's possible the boat had a modified hitch, which resulted in the detachment. A police source tells the News, "It wasn’t properly secured."

Neighbors called that stretch of Hylan Boulevard dangerous, telling the Advance, "It's life or death over here," and "It's crazy—I can't let my kids go too close to the street because you don't know when a car is going to come and hit them."