With the 8-year-old boy whose school bus antics led to the death of a classmate being held in a diagnostic testing facility, Mayor Bloomberg is questioning the wisdom of pursuing criminal charges against such a young child.

The boy, Tafiri, whose last name was not disclosed because of his age, apparently snuck onto a locked school bus and released the parking brake, causing it to roll forward and kill Amber Sadiq, 8, a classmate at the nearby P.S. 161 in Crown Heights on Monday afternoon. Police arrested him on charges of criminally negligent homicide, but there is now growing sentiment that the charge was too severe.

The chief spokesman for the police department declined to comment on the decision to charge Tafiri.

Prosecutors typically handle criminal cases, but because of the boy’s age his case is being handled in Family Court by the Corporation Counsel of the city’s Law Department, giving the mayor control over the case. Mr. Bloomberg also appoints the commissioner of the city’s Administration for Children’s Services, which is evaluating the boy’s psychological state.

“This is an 8-year-old child,” Mr. Bloomberg said yesterday.”I don’t know what facing charges means, but we’re going to talk to the family court judge and to ACS and see what we can do.”

Juvenile justice experts backed the mayor’s sentiments.

“The notion that you would charge an 8-year-old with homicide, whether it’s negligent or intentional, seems crazy to me,” a professor of psychology at Temple University who specializes in the juvenile justice system, Laurence Steinberg, said. “What he probably can grasp is that he did something wrong and that something bad happened. Whether he’s able to understand that what happened was because of something he did is another question.”

Statistics indicate young children rarely face prosecution in New York State. A spokesman for the state’s Office of Children and Family Services, where youth offenders between ages 7 and 15 often serve terms in “residences” if they are prosecuted, said the agency typically receives nine or 10 offenders under age 12 every year.

Among those who oppose prosecuting Tafiri are members of the victim’s family, who held a private funeral service for her in Queens yesterday. A City Councilwoman from their neighborhood, Letitia James, called the initial charges against Tafiri a “rush to judgment.”

An attorney for the boy, Samuel Karliner, said if prosecutors charge his client with criminally negligent homicide, the boy could face up to 18 months in a nonsecure facility run by the city. “It was tragic what happened, but that doesn’t mean you need to find someone is criminally responsible,” Mr. Karliner said.

Officials believe Tafiri was able to sneak onto the bus because state law prohibits drivers from locking emergency exits, which can be pried open from the outside.