WARWICK — One moment, 15-year-old Kimberly Pisaturo, a smart and popular sophomore at Pilgrim High School, was walking to school, looking down at her cell phone, witnesses say, when she stepped into a crosswalk running alongside busy Warwick Avenue and into the path of a turning school bus.

She died there Friday morning before the 7:24 first bell sounded just up the street.

“For someone this young to lose their life is a tragedy of unmeasurable proportion,” School Committee member Paul Cannistra said hours later, long after firefighters had removed the red tarp encircling the place behind the bus where Kimberly’s body had lain, and the intersection of Warwick Avenue and Pilgrim Parkway had resumed its hectic pace.

The accident happened around 7:05 a.m.

Police Chief Stephen M. McCartney said the bus, carrying about 20 Pilgrim students, had been driving north on Warwick Avenue. It stopped at the intersection. On a green light, it turned left onto Pilgrim Parkway heading for the high school about a quarter-mile away.

Witnesses told the police Kimberly appeared to be looking at her cell phone and had her head down when she walked into the crosswalk as the bus was turning in, McCartney said. Earphones and an iPod were also found on her, he said in a statement; it wasn’t clear whether she had been listening to music.

Kimberly may also have been wearing the hood of a sweatshirt pulled up, said School Supt. Peter Horoschak.

The superintendent said a teaching assistant in a car behind the bus noticed the imminent accident and blew her horn to warn Kimberly “but it happened so quickly.”

Horoschak said some of the students on the bus also reported seeing the girl and the bus on a collision course and at least one bus rider heard the bus hit the student.

“This is a tremendous loss,” said Horoschak. “She was an extraordinarily good student, very well liked, and her academic standing was excellent.”

Dozens of grief counselors from other city schools converged on the high school to offer help to the 1,200 students.

Horoschak described the mood at the school as “very somber.” He added, “It’s a very shocking thing to have occurred.”

Some students asked to be released early, he said, while counselors spoke to the remaining students in small groups.

Through the police, Kimberly’s family issued a statement saying they appreciated “the outpouring of public sympathy and would only ask for privacy during this very difficult time.”

While a police reconstruction team investigated the accident Friday morning, the bus driver, described by Horoschak as distraught, sat 20 yards away in the back seat of a car, consoled by several weeping women. “It’s a very difficult matter for her to be dealing with,” he said.

McCartney said the police had not charged the driver, Rebecca L. Toolin, 28. The accident remains under investigation.

A spokeswoman for the First Student bus company said Toolin has been suspended pending the outcome of the investigation, and that the company is cooperating with local authorities. Toolin’s history with the company was not released.

“It’s a tragic accident and we are deeply saddened,” said spokeswoman Nicole Jones. The national bus company operates about 60,000 school buses in 41 states, Jones said. Fatalities are “rare, but too many,” she said.

The last fatality involving a First Student school bus was in January 2009, when a seventh-grader in Northampton, Pa., was crushed when he fell under the wheels of a bus as he and friends were going to school.

The last time a student was injured in a school bus accident in Rhode Island was in early April, when a 12-year-old girl ran across the parking lot at Joseph H. Gaudet Middle School in Middletown and was struck by a slow-moving school bus owned by First Student. The girl recovered; the driver was not charged.

With reports from Richard C. Dujardin and Amanda Milkovits

tmooney@projo.com