An 88-year-old patient and a 36-year-old employee are dead after a gunman opened fire in a Florida hospital Sunday, an attack that police believe was at random.

David Owens, 29, entered Parrish Medical Center at 2 a.m. through the emergency room and went to the third floor, where he used a handgun to fatally shoot patient Cynthia Zingsheim and employee Carrie Rouzer, who was sitting with Zingsheim in her room, Florida Today reported.

He has been booked into the Brevard County Jail on two counts of murder, the Orlando Sentinel reported.

Owens, of Titusville, Florida, has a history of being detained for mental health observation, and is known to law enforcement after a series of arrests ranging from drug possession to battery, authorities said.

According to the Sentinel, Owens was found guilty of battery on a police officer in 2011; a judge ordered him to undergo a mental health examination twice in 2012. He was also arrested for cocaine and marijuana possession and domestic battery, which were dismissed.

"Investigators have not been able to determine a motive at this time, nor any connection to the victims," said Commander Todd Hutchinson in a news release. "They are continuing to investigate this tragic incident."

Moments after Owens opened fire in the third-floor room, two unarmed hospital security guards took the suspect down,  CNN reported. They held him until police arrived.

"I cannot stress enough, the response of the Parrish Medical Center staff, without a doubt, saved more lives," Titusville Police Chief John said.

Lau said the hospital is operating "business as usual."

"They're heavy-hearted right now. They lost a member of their team."