By Rachel Leigh| February 8, 2013 at 10:20 PM EST - Updated July 25 at 8:16 PM
WEST PALM BEACH, FL (WFLX) - After two separate shootings of bicyclists on West Palm Beach streets, police have arrested a man who they say claims he "heard a voice tell him to go kill someone".
Rupert O'Neil Harty, 31, has been charged with first-degree murder in the Dec. 22 shooting death of Amaria Grant.
Harty has also been charged with attempted murder in the Feb. 1 shooting of a male bicyclist at the intersection of Broadway and 48th Street in West Palm Beach, according to Capt. David Berhardt.
The still unidentified victim was rushed to St. Mary's Medical Center with 'serious' gunshot wounds, and is still alive, Bernhardt said. Police were looking to question the occupant of a taxi cab in connection with that shooting.
Investigators say Grant, who was working as a nanny, was on her bicycle on South Olive Avenue near Edmor Road when Harty approached her and opened fire three days before Christmas.
Grant died from multiple gunshot wounds at the scene.
According to police documents, Harty told investigators he was sitting at his home on December 22, when he 'heard a voice tell him to go kill someone.'
Investigators say he drove in his taxi cab for about twenty minutes before parking on a side street and walking up to Grant while she was on her bike.
Documents show that a 9mm handgun may have been used in that shooting. Grant left the scene in the cab and drove home, documents show.
Harty was arrested on an unrelated charge on Thursday night and interviewed by detectives at the West Palm Beach Police Department. It was at that time that police say Harty confessed to killing Grant.
He was denied bond at his first court appearance Friday. Police are still investigating both shootings and do not anticipate any other arrests.