By Jonathan Allen

NEW YORK (Reuters) - New York police have charged a man in the weekend stabbing of two children, one of them fatally, in the elevator of a Brooklyn housing project, officials said.

Daniel St. Hubert, 27, was charged on Thursday evening with murder in the death of Prince Joshua Avitto, 6, and attempted murder in the stabbing of Mikayla Capers, 7, along with assault and various weapon and graffiti charges, according to police.

Mayor Bill de Blasio has used the attacks to highlight poor security in some of New York's public housing and the justice system's shortcomings in dealing with the mentally ill.

St. Hubert was released from state prison on parole last month after serving a five-year sentence for trying to strangle his mother. He is being investigated for two other recent stabbing attacks in the city.

"This is someone who probably had very severe mental health problems, and I don't know why those were not caught and treated earlier," de Blasio said on Thursday evening." Our larger prison system in New York State, our prison system all over the country, does not address mental health issues effectively."

St. Hubert was arrested on Wednesday evening about 15 minutes after de Blasio held a news conference with police where he released St. Hubert's mug shot and promised to install more surveillance cameras in public housing projects.

The children's families said the pair were close friends who going out for ice cream on a hot Sunday evening when they were attacked. The girl remained hospitalized.

Authorities say St. Hubert, who lives in Brooklyn, may have been behind the stabbing death of an 18-year-old woman last week and the non-fatal stabbing on Wednesday of a man on a Manhattan subway platform.

(Reporting by Jonathan Allen; Editing by Doina Chiacu)