A family acquaintance was behind the wheel of a pickup truck that struck and killed a 14-month-old boy in Mashpee Friday evening, as officials continued their investigation into the accident, the town’s police chief said Saturday.

Police and firefighters were called around 5:27 p.m. Friday to a Coombs Lane home, where responders found the boy suffering from “very critical’’ injuries after he was hit by the truck.

The boy was transported to Falmouth Hospital by ­Mashpee Fire Rescue, but he died of his injuries a short time later, police said.

The driver of the truck remained at the scene, police said.

On Saturday, Mashpee police Chief Scott Carline told the Globe in a phone interview that officials expect to complete their investigation by the middle or end of the week. Part of the investigation will focus on whether the truck was functioning correctly at the time of the accident, Carline said.

“Once we complete the investigation, we will confer with the [Cape and Islands district attorney] to determine if charges will be filed,’’ Carline said.

A spokeswoman for the Cape and Islands district attorney’s office said Saturday the matter remains under investigation.

Carline declined to comment further on the investigation or the identities of people involved but described the accident scene Friday night as chaotic.

“This one is the worst I’ve ever seen in 29 years’’ as a police officer, Carline said.

In a statement, police said the accident is being investigated by the Mashpee Police Department detective bureau and the Cape Cod regional crash reconstruction team.

In the same release, Mashpee police said their “thoughts and prayers go out to the victim and his family at this time.’’

John Hilliard can be reached at john.hilliard@globe.com.