Dallas police said that a 9-year-old boy has shot and killed an 11-year-old boy in a Walmart parking lot on Sunday.

Police said that a 32-year-old woman parked at the Walmart and left the two boys in a car while she went shopping. Police believed that the 9-year-old boy found the gun inside the vehicle, WFAA reported.

The older boy was taken to a hospital, where he was pronounced dead. Both the two boys' identities have not been released, and they were reportedly not related.

In Houston, a shooting involving two minors also took place when a 3-year-old boy got his hands on a gun in their apartment. The toddler has shot his 8-month-old brother to death.

Houston Police Assistant Chief Wendy Baimbridge said that adults were in the apartment at the time of the incident. They drove the 8-month-old baby to a hospital, but he did not survive, Crime Online reported. The baby was reportedly shot in the abdomen.

"I just want to take this moment and plead with parents and guardians all over to not allow your firearms to be accessible to anyone in the house. Lock them up. There are things that you can do to render that weapon safe," Baimbridge said in the report.

Detectives could not find the gun used in the shooting at first. However, it was later discovered in the vehicle that the family members used to rush the infant to the hospital.

READ NEXT: Gun Violence and Its Impact on the Latino Community

Children and Accidental Gun Deaths

A 2016 report found that minors died from accidental shootings during the first six months of the year, may it be at their own hands or at the hands of other children or adults, CBS News reported. 

Deaths and injuries increased for children under five, with 3-year-olds the most common shooters and victims among young children. 

It was also found that states in the South are among those with the highest rates of accidental shootings that involve minors. In addition, the majority of shooters and victims are boys.

In 2014, the U.S. Centers for Disease Control and Prevention (CDC) had reported that 74 minors died from the accidental firing of guns.

In 2020, deadly accidental shootings by children increased by 43 percent in March and April as compared to average gun deaths over the last three years, according to another CBS News report.

Gun safety advocates are concern that with schools closed and children facing boredom and isolation due to the pandemic, there would be an increased risk of finding unsecured guns in their homes.

"It could create more opportunity for kids to gain access to guns and unintentionally hurt themselves or someone else," Shannon Watts, founder of Everytown's anti-gun violence volunteer network Moms Demand Action, said in the report.

Accidental shootings by children under 17 in March and April last year resulted in 21 deaths, comparing to an average of 15 deaths during the same period between 2017 to 2019.

The National Shooting Sports Foundation said firearm sales peaked at more than 2.3 million in March, an 80 percent increase from March 2019.

READ MORE: 13-Year-Old boy Arrested for Shooting Younger Sister to Death

WATCH: How U.S. Gun Deaths And Mass Shootings Compare To Other Countries -from NBC News Now