WEST PALM BEACH, Fla. – A Florida man who randomly beat to death an elderly woman after taking the hallucinogenic drug flakka has been sentenced to life in prison.

The Palm Beach Post reported Monday that 29-year-old Derren Morrison was sentenced on second-degree murder charges by Circuit Judge Cheryl Caracuzzo for the 2015 death of Louise Clinton. The grandmother died on her 83rd birthday.

Morrison told investigators he smoked flakka hours before the attack. Relatives said he was claiming someone was about to kill him.

He went to Clinton's home, knocked and began beating her as soon as she opened the door. He told police he thought Clinton was a blood-covered demon who was trying to kill him.

Flakka is known to cause paranoia and delusions. The sentencing happened Friday.