Rigoberto Lopez, 21, was taken into custody by New York City police on Saturday
Police sources said Lopez, who is mentally ill, was charged on Sunday with murder and attempted murder after confessing to four separate attacks
Subway rider, 67-year-old male, was wounded in stabbing on Friday before noon
Twelve hours later, a man was fatally stabbed in neck, torso in southern Queens
Two hours later, a woman, 44, died from stab wounds after she was found
Minutes later, another man, 43, was wounded in stabbing in 181st Street station