Police believe a mother killed her 5-year-old son before committing suicide early Saturday inside a Mesa, Arizona, hospital where the child was being treated.

The bodies of Lola Griffith, 27, and her son, Helious, were discovered in his room by hospital staff at Cardon Children’s Medical Center at 2 a.m. local time, Mesa Police Department Det. Steve Berry told NBC News.

Mesa police are investigating the incident as a murder-suicide, Berry said. "We don't have any reason to believe that it is not," he added.

Cardon Children’s Medical Center in Mesa, Az. KPNX

Nurses who check on patients every two hours discovered Griffith with a fatal gunshot wound, Berry said. Police were not disclosing what killed 5-year-old Helious.

Berry said nurses reported that the mother and son were fine at midnight.

Berry wouldn't say what the 5-year-old was being treated for, citing patient privacy.

He said no one else in the hospital was affected by the violence. "Everything was kind of confined to that one room," he said.

Banner Health, which owns Cardon Children’s Medical Center, said in a statement that each of their health care centers have a policy that prohibits weapons of any kind.

"The safety of our patients, associates and visitors is paramount to us and is our top priority," the statement said. "Our thoughts are with the family and their loss at this time."