Shawn Smith

A Brooklyn man who allegedly threw his 4-year-old brother off a roof had a history of mental illness according to his family.

Shawn Smith, 20, faces murder charges after he tossed little Shimron Smith from the roof of a 7-story building where the family lived in Brooklyn.

Shimron’s 5-year-old brother Steven, who was in the apartment, was not injured.

Authorities says Smith calmly flagged down a patrol car and confessed about 45 minutes later.

Smith led officers to his brother’s broken body in the courtyard of the apartment building on Norstrand Avenue near Avenue K around 3:30 AM on Saturday.

Family members tell the NY Daily News they saw red flags in the months before the tragedy.

“You could see in his eyes, he was deteriorating,” said Robin Frith, who is married to Smith’s grandmother.

Family members say Smith broke down a heavy door in his mother’s Flatland’s apartment. The frightened woman called 911 and begged for help.

Kings County Hospital’s psychiatric crisis team visited the home but Smith refused to speak to them.

Smith was admitted to Kings County Hospital for an emergency psychiatric evaluation. He was diagnosed with schizophrenia and released home after being stabilized on psychotropic medications.

“He spent three weeks there and when he come back, he was okay.” His mother, Odessa Frith, told The News on Sunday.

Smith was all smiles during his perp walk outside the 70th Precinct on Saturday.

“I’ve finally become a criminal!”, Smith told reporters gathered outside the station house.

It isn’t clear if Smith was still taking his medications prior to the tragedy.

Noncompliance with medications is a major problem with psychiatric patients who stop taking their medications because they don’t believe they are sick.