3-month-old dies after being left in hot car in Houston, police say

A baby boy died in Houston on Tuesday after being left in a car amid a dangerous and unrelenting heat wave, police said.

A mother and her two children arrived in the afternoon for a visit at the Harris Center for Mental Health and IDD in Houston, the public mental health authority for Texas' Harris County. She went into the building with her 4-year-old but left her 3-month-old alone in the car, according to the Houston Police Department.

When the mother and toddler returned to the car sometime later, getting ready to leave, she found her baby unresponsive inside. It was unclear how long the child was left unattended in the vehicle and whether it was intentional or by mistake, police said.

First responders arrived on scene within minutes of receiving the 911 call and attempted life-saving measures. The baby was subsequently transported to a nearby hospital where he was pronounced dead, according to police.

Houston Police Assistant Chief Yasar Bashir described the incident as tragic but "avoidable," saying it "should never happen."

"Houston gets very hot and under no circumstances you should leave a child in a car, not even for a moment," Bashir said during a press conference on Tuesday evening. "Especially an infant or a child, the body temperature goes up very quickly"

The Harris County medical examiner will conduct an autopsy and determine the cause of death.

Authorities could bring charges depending on what the investigation reveals, according to Bashir, who noted that both parents are being cooperative with detectives.

"We are still in the early stages of our investigation," he told reporters. "When a child passes away, you want to slow down the investigation and make sure you don't miss anything."

Much of Texas was under heat alerts on Tuesday as scorching temperatures continued to plague the southern United States. The heat index value -- a measure of how hot it really feels when relative humidity is combined with the air temperature -- was forecast to reach 108 degrees Fahrenheit in Houston by the afternoon.

Heat index values are expected to be around 110 degrees from Texas to Florida through the end of this week. And the latest weather forecast shows no end in sight, with hotter than normal temperatures expected to persist for the South through the middle of August.

ABC News' Melissa Griffin, Michelle Mendez and Gina Sunseri contributed to this report.