A stranger threw a 7-year-old boy to the ground Thursday in the New York City borough of Queens in an unprovoked attack, his family said.

The boy, who lives in Long Island, was waiting for a pizza delivery on his grandparents' porch in Kew Gardens when he was badly injured in the attack that happened about 4:15 p.m., NBC New York reported.

A 35-year-old man, Laurance Gendreau, was arrested and has been charged with assault, acting in a manner injurious to a child younger than 17 and harassment, according to the New York City Police Department.

The boy was walking with his parents when Gendreau, who was walking in the area, suddenly picked up the child and threw him to the ground, police said. The boy was taken to a hospital and was being treated for hemorrhaging to the brain and a contusion to the head, officials said.

Police in a statement said they responded to a report of an emotionally disturbed person.

The boy's grandfather, Naftali Portnoy, told NBC New York that the suspect said "I'm bipolar. I wanted to kill the kid," and that the man had been bothering other people on the block Thursday before the unprovoked attack.

It was not clear if Gendreau had an attorney who could speak on his behalf. Police said in a statement that Gendreau is "undomiciled," or homeless.