Homeless man arrested for vicious beating in NYC train station

How could this crime have been prevented? Were there any warning signs? Any possible hints of what was coming? Any chances to go ina  different direction?

In 1995, Foster was arrested as a 14-year-old for killing his own 82-year-old grandmother in Flatbush, Brooklyn. He apparently got into a dispute about money and started punching her. She died on the couch shortly after the attack. …

In 2010, police arrested him for stabbing a 50-year-old woman at a psychiatric center in Queens Village. The woman was left permanently disfigured in the attack.

Foster was paroled last year for that incident.

New York City Police arrested him in August for Petty Larceny. The next day he was arrested again for criminal mischief.

Nope. Nothing at all that could have been done. There were no chances to have nipped this in the bud.