3 mowed down on B’klyn roads

TRAGEDY STRUCK three times Monday in Brooklyn, when a beloved grandfather, a dad picking up his son from day care and a bicyclist were mowed down in separate accidents.

The roadside carnage began just after 1 p.m., when a dump truck driver ran over Rafael (Rafie) Nieves, 85, outside his Williamsburg home and then drove off as horrified witnesses banged on the vehicle.

Even so, investigators don’t believe the 45-year-old driver, whom cops say they located Monday night, realized he had hit the pedestrian, police sources said. No charges were filed.

Nieves was crossing Grand St. near Lorimer St. when the truck hit him.

“He was crossing the street after he went to the supermarket,” said Victoria Brito, 44, who works at a hair salon on the first floor of the victim’s building. “When we came out, the truck had already passed him, run him over, and he was behind the truck.”

Nieves, a military veteran and native of Puerto Rico, had two children and five grandchildren, his daughter said.

“He was our leader, our guardian. He provided for us 24/7. He will be dearly missed,” daughter Maritza Nieves said.

At 4:45 p.m. a man walking his bicycle through a Brooklyn intersection was killed when he tried to maneuver

Battered car sits at Avenue A and Linden Blvd. in East Flatbush, Brooklyn, after driver lost control, hit five vehicles and killed pedestrian Marlon Palacios, leaving victim’s shoe in street (r.).

around a box truck on Avenue X near Coney Island Ave. in Sheepshead Bay.

The unidentified man may have slipped beneath the truck after he emerged from between two parked cars, cop sources said.

The third fatal accident happened in East Flatbush, when a man apparently suffering from a medical episode lost control of his silver Pathfinder, hit five cars and struck Marlon Palacios, 43, who was on his way to pick up his 4-year-old son at a day care center at about 5:20 p.m., according to authorities and family.Palacios’ distraught relatives rushed out to Avenue A and Linden Blvd. after the hardworking maintenance man and father of two didn’t come home and didn’t pick up his phone.

They saw the wreckage, and cops corralled them into the nearby Coconut Grove Childhood Education Center to break the awful news.

“He was the sweetest man in the world,” Palacios’ sister Edna said, adding that he worked in Manhattan and lived near the crash scene. Palacios also had a 9-year-old son.

“I can’t believe it. I don’t know what I’m going to tell our mother. I can’t believe it,” his sister said through tears.

Including Monday's deaths, police say six pedestrians and one bicyclist have been killed on the city's streets so far this year. A CAR ON the LIRR tracks was slammed by a westbound nonpassenger train in Brentwood, killing the driver, Suffolk County officials said Monday.

The 8 p.m. crash occurred at the Fourth St. crossing west of the Brentwood station, authorities said.

A railroad spokesman had no other details.

Gov. Cuomo said the victim was the only occupant in the vehicle and no train crew members were injured.

Service was temporarily suspended.