CHICAGO (CBS) — A mother and her two children were found dead in their home in northwest suburban Lake in the Hills on Tuesday afternoon, in what authorities said appears to be a murder-suicide.

Just before 3 p.m. Tuesday, police and firefighters received a call of an unresponsive person in a home in the 2300 block of Daybreak Drive in Lake in the Hills. When firefighters arrived, the home was locked, so crews broke down the door, and found three people dead inside.

The victims have been identified as 27-year-old Carla Lopez-Mejia, 11-year-old Ezequiel Garcia, and 8-year-old Ariana Garcia.

The McHenry County Coroner’s office said preliminary findings suggest the deaths were a murder-suicide. Complete autopsies and toxicology tests were scheduled for Wednesday afternoon.

Neighbors were stunned by the deaths. They said the mother kept to herself and was very quiet, they never imagined something like this could happen.

“It’s shocking for something like this to happen right next door,” said neighbor, Janaya Simmons. “I didn’t get any sleep. I’ve been thinking about them. Is there something I could have done?”

Janaya Simmons said her daughter would often play with the two kids. That is why she placed balloons and candles outside the home in their honor.

“Ariana and Ez were very playful, very nice and they were always out here playing no matter what type of weather, just a joy,” Simmons said.

Monicia Brown’s cousin often played with the two children. She watched in horror Tuesday as her worst fears were realized next door.

“It’s shocking,” Brown said. “I don’t believe it. They live right next door. My cousin played with the little girl. I knew them, so that’s why I’m just like, I have never been this close to death before.”

Brown said the mother had seemed to be depressed lately. She last heard from the mother on New Year’s Day.

“I just always saw her sad. These last few weeks, I saw her sad, and when I went over there on New Year’s – because I needed to grab a safety pin for my New Year’s dress – the little daughter answered the door, and the mom was like, ‘Tell her, no, we don’t have any,’ and I’m like, ‘Alright, happy holidays, guys,’ and that was actually the last time I seen or talked to the mom,” she said.

Ezequiel was a sixth graders at Marlowe Middle School, while Ariana was a third grader at Martin Elementary School.

In a statement, the superintendent of Huntley District 158 said, “this tragedy has affected all of us in the Huntley 158 family, and the grief that accompanies news, such as this, will take time to process.”

“I’m just sad for her, sad for the kids,” said neighbor Jennifer Goodrich. “And you don’t really know what to tell your kids in that situation.”

The school district has offered parents advice on how to help children with the grieving process. They are also providing counselors throughout the day.

Lake in the Hills police emphasized that there is no threat to the public.