DuPage County authorities are helping police in the investigation. Investigators are not yet calling it a murder-suicide, but they said residents in Westmont should not be worried about some random killer on the loose.
Friday night, Westmont police gathered evidence at a second-floor apartment in the 500-block of West 61st Street. Earlier in the morning, the bodies of 6-year-old Julia Moore, her 51-year-old grandmother Linda Brennan, and Brennan's ex-husband, Mark Chapman, were found.
"This was an isolated incident. This was not a random act that this incident was confined mainly to this apartment and affecting this family only," said Westmont Police Chief Thomas Mulhearn. "The residents should not be aware that this was a random act, that there's somebody out running around."
Police recovered a handgun in the living room where the two adults, Brennan and Chapman, were found dead. Investigators have not yet identified the shooter.
Officers had initially come to the building after relatives and the child's school requested a well-being check.
Neighbor Frank Slowik entered through a window after police couldn't get in. He found Brennan and Chapman dead on the couch.
"The family was a really good family, very easygoing, they definitely loved and cared for their granddaughter," said Slowik.
Officers found the body of Julia Moore in a bedroom.
Police said Brennan and Chapman had divorced some time ago, but had reconciled and were living together with Julia.
"It's hard to comprehend the loss of any life, especially when it comes to a young girl like that," said Slowik.
Police have not determined when the shootings took place, but Slowik said he heard loud gunshots around 1 a.m. on Wednesday. At the time, he thought they were fireworks.
Investigators said they are waiting for autopsy results Saturday before offering more details.
