An out-of-control car plowed into dozens of trick-or-treaters and their families on a Bronx street Saturday, killing two adults and a child, and injuring three other people.

The casualties are all members of two extended families.

Luis Perez, 65, died, along with his 9-year-old granddaughter, Nyanna Aquil.

His 3-year-old granddaughter, Jasmina Aquil, was among the injured.

Perez, who was retired, was “an incredible man,’’ said his friend, Justin Mendez.

“He’s always with his grandkids — all he does is take care of them.’’

Also killed was Kristian Leka, 24, a truck driver.

“He was on the sidewalk trick-or-treating with his 9-year-old sister,’’ said a cousin, who asked not to be identified.

The car that hit his cousin, he said, “was speeding, hit another car and then flipped onto the sidewalk.’’

A close friend of Leka, who also asked that his name not be printed, said before the car struck Leka down, he desperately tried to push his sister, Fiona, out of the away.

Also hurt was Greata Leka, 21.

All of the injured were listed in critical condition.

One of the 9-year-old girls who was hit had been dressed as a cheetah; the other as a princess.

The driver of the car, Howard Unger, 57, was also being treated at Jacobi.

Police believe he lost control of the vehicle after suffering a seizure or experiencing some other medical problem.

The horror happened at 4:50 p.m. when Unger’s car began speeding down Morris Park Avenue near Radcliff Avenue in the Morris Park neighborhood.

Charlie Castagnozzi, who was with his wife and three kids, heard a car “accelerate.’’

“I turned around and I saw that [the driver] hit the car in front of him,’’ he said.

Castagnozzi said the vehicle then sideswiped a bus before crashing through a metal fence and winding up in the front yard of a home.

He saw, to his horror, a fatally injured man lying in the street.

“I also saw a little girl on the ground,’’ he said.

“She was having trouble breathing. They put her in an ambulance.’’

Johnny Ha, 14, was walking to his home on Morris Park Avenue, when he saw a damaged car in his front yard.

When he got closer he saw “two or three adults and two kids lying on the ground,’’ he said.

“I was traumatized, scared and afraid,” he said. “I didn’t know what to do.’’

Witness Kristina DeJesus, who had been returning to her home from a market, said, “I saw two little girls trick-or-treating. This is a family neighborhood.

“The car flew over the curb [and] hit the gate.’’

During its out-of-control ride, she said, the vehicle hit the girls and two men.

I saw a torso on the sidewalk. I didn’t know if it was a Halloween dummy or a real person - Fabio Cotza, witness

One of the men had his legs “completely torn off,’’ she said.

“I dropped my bags and ran over. Everybody stopped trick-or-treating, saying, ‘how can we help?’ ’’ she said.

“They couldn’t believe this was happening on Halloween. There’s nothing but kids out there.’’

Fabio Cotza, who witnessed the tragedy from his apartment across the street, said, “I was completely in shock. I was thinking, ‘This is not real.’”

“I saw a torso on the sidewalk. I didn’t know if it was a Halloween dummy or a real person.”

Cotza said, “I just grabbed a whole bunch of towels and ran outside. I saw people standing over a little girl screaming, ‘She’s going to die! Don’t move her neck.’”

Another witness, Kayla Destiny Mojica, wrote on Facebook, “Sad day . . . Just saw a bunch of ambulance trucks and policemen carry a little girl on a stretcher as she screamed.’’

Additional reporting by Leonica Valentine, Aaron Short, Amanda Woods, Megan McGibney and John Roca