Residents on Whitten Street in Dorchester heard piercing screams late Sunday morning and then watched in horror as rescuers in the middle of the street tried to revive a 5-year-old boy who had been struck by a vehicle, witnesses said.

Boston police said the boy, whom authorities did not identify, was hit shortly before 11:45 a.m. on Whitten Street. He was rushed to Boston Medical Center with life-threatening injuries, said police.

The driver had not been cited or charged as of Sunday evening, they said. The child’s condition was not known.

Tammy Davis, 44, a neighbor on the narrow, one-way street, said she heard screaming and came outside to find rescuers performing chest compressions on the boy.

“You just knew that it wasn’t working,’’ an emotional Davis said.

She said the boy lives with his grandmother, who was distraught after the accident.

“The grandmother was completely overwrought,’’ Davis said. “She was gone.’’

The light blue, mid-sized Chrysler that struck the child was parked at an angle from the curb as police investigated. Neighbors said the occupants were a woman and two men.

“That poor girl,’’ Davis said of the woman. “That girl was bawling.’’

The street can sometimes be dangerous, many neighbors said.

“I wish that there was some way that the cars would actually be able to slow down at this road,’’ she said. “Because they go so fast.’’

Officer Nicole Grant, a Boston police spokeswoman, could not say how fast the car was traveling when it struck the boy, and she had no information on prior accidents on the street, which has at least two yellow signs warning drivers to proceed slowly.

The speed limit on thickly settled residential streets in the city, unless otherwise noted, is 30 miles per hour, Grant said. Whitten Street has no signs indicating its speed limit.

“Summertime, you better slow down when you come down a small street,’’ said neighbor Phoung Dao, 39, who has two young sons. He said Sunday’s accident made him fearful for their safety.

“My [older] kid, he plays out around here,’’ Dao said.

Police officers at the scene spoke with witnesses and combed the street for evidence as one drove the Chrysler in reverse and forward, stopping repeatedly as measurements were taken. The vehicle was placed on a flat-bed truck and removed shortly before 2:45 p.m.

A neighbor who declined to give her name said the boy was bleeding from his head before rescuers arrived.

“I even checked his pulse; I didn’t get any,’’ said the woman, who identified herself as a nursing assistant.

She said the boy was with another child at the time of the accident who was not hurt; police could not confirm that report.

The woman said the boy is always with his grandmother, who told her after the accident that she had warned the children to wait for her before crossing the street to reach her vehicle.

Neighbor Stevee Davenport, 22, said rescuers gave the boy cardiopulmonary resuscitation constantly, even as they placed him in an ambulance.

“The whole time he was on the ground they never stopped,’’ Davenport said. “It’s very sad, I’ve never seen anything like that.’’