A man charged with stabbing four people, two fatally, in the New York City subway system was ordered held without bail Monday.

Rigoberto Lopez was arraigned on murder and attempted murder charges. A court complaint said he confessed to the attacks.

A message seeking comment was left for Lopez’s attorney.

One victim was discovered dead on a subway train in Queens late Friday with several stab wounds to his neck and torso, police said. Two hours later, a 44-year-old woman, Claudine Roberts, was found stabbed to death in a subway car in upper Manhattan.

Her father, Winston Roberts, told the New York Post that she struggled with mental illness since her teens. She had had been living in a shelter after recently getting out of a hospital, but she stopped by his home just Wednesday, he said.

“I loved my daughter,” he said. “I tried to do the best for her.”

Lopez is also charged in two other attacks in upper Manhattan subway stations late Friday and early Saturday. The victims, both men, survived.

Authorities believe all four victims were homeless.

Police leaders said they would deploy an additional 500 officers into the subway system to guard against future assaults. Transit officials are asking for another 1,000 officers.

(AP)