Detroit ? A 5-year-old boy called 911 to report that his mother had collapsed in their apartment, but an operator told him he should not be playing on the phone, and she died before help arrived.

The family of Sherrill Turner, 46, does not know whether a swifter response could have saved her life, but relatives want to know why the operator apparently treated the call as if it were a prank.

Police said the 911 response was under investigation.

Turner’s son, Robert, placed two calls to 911 after his mother collapsed Feb. 20 on the kitchen floor. During one of the calls, an operator said, “You shouldn’t be playing on the phone.”

In a tape of the call, parts of which were broadcast by Detroit-area television stations, the operator said, “Now put her on the phone before I send the police out there to knock on the door and you gonna be in trouble.”

The 911 operator remains on the job amid the investigation.