NEW YORK (CBSNewYork) — A young child is in critical condition after being brutally attacked by a homeless person in Queens.

According to police sources, the homeless man was on Metropolitan Avenue and Lefferts Blvd. in Kew Gardens when he picked up a seven-year-old boy and then slammed the child’s head into the pavement just before 5 p.m.

CBS2’s Lisa Rozner has learned the child and his 10-year-old brother were waiting for a pizza delivery outside when the 35-year-old man approached them and launched the unprovoked assault.

“You heard that scream, you knew something serious was going on, it’s a kid that was picked up and smashed to the ground, nothing less than that,” the child’s grandfather Naftali Portnoy said.

Portnoy told CBS2 he saw the suspect — who he says was shirtless at the time — and followed him for more than two blocks towards Lefferts Blvd.

“I went after him, followed him, called 911, the police found him… He did say ‘I’m bipolar’ his first words were ‘I’m bipolar’ and something about ‘kill the kid’ wanted to kill the kid,” the grandfather added.

That suspect was arrested by officers responding to the violent scene. He has been taken to Jamaica Hospital for a mental evaluation as the investigation continues. Police say the man is emotionally disturbed and homeless.

The attacker has been identified by police has Laurance Gendreau. The 35-year-old is now facing multiple charges including assault and harassment.

The child was rushed to an area hospital with what police describe as serious head injuries. Authorities tell CBS2 the boy’s condition has been stabilized, but he is still listed as critical. CBS2 has learned the boy has brain hemorrhaging and injuries to his face.

The vicious attack comes just days after another homeless man was arrested in Manhattan for allegedly murdering four men as they slept on the streets of Chinatown.

Stay with CBS New York for the latest on this developing story