The homeless man charged in a 12-hour stabbing spree earlier this week is being held without bail on four counts of attempted murder.

Kenny Alexis is also facing assault, robbery and weapons charges. Investigators say he confessed to stabbing four people between Tuesday evening and early Wednesday morning, but claims he was provoked each time.

Alexis' attorney asked the judge to allow a psychiatric evaluation. His lawyer says Alexis is unable to participate in his own defense.

Police still don't know exactly what provoked the attacks, which began on a C train in Morningside Heights. Houston tourist Christopher McCarthy, 21, was stabbed in the chest and remains in critical condition.

Alexis has also been charged in the stabbing of 30-year-old Ambrosio Castro of Brooklyn inside the Rockefeller Center subway station early Wednesday morning.

An hour later, two Canadian tourists were stabbed in Times Square. Alexis was taken into custody shortly after that.

A judge in Boston released Alexis on his own recognizance just five days before he went on his alleged stabbing rampage.

He is due in court in Massachusetts next week to face a series of misdemeanor offenses.