A 3-year-old and his 6-year-old brother were among four people shot and wounded when shots were fired at a crowd outside a Bronx park Tuesday evening, the New York Police Department said.

Hundreds were gathered at the St. James Park when two people wearing all black and masks pulled up on an "illegal scooter" around 6 p.m. and one of them got off and fired into the crowd, striking the four victims, NYPD Chief of Patrol John Chell said at a media briefing Tuesday night.

Both children were shot in their legs, Chell said. A 23-year-old man was shot multiple times and a 25-year-old man, believed to be his cousin, was shot once in the back, he added.

All four victims are "doing well" and are expected to recover from their injuries, the chief of patrol said Tuesday night.

After the shooting, the suspects fled on the scooter and authorities were working on identifying them Tuesday evening. Police said the incident was captured on video.

It remains unclear what motivated the attack, or whether the suspects knew any of the victims. "We don't know who they were shooting at -- there was hundreds people in the park," Chell said.

He called the shooting "totally unacceptable."

"As a dad and a parent in the city, I couldn't imagine this happening to my kids. Absolutely heart-wrenching and disturbing," Chell said.

The shooting comes days after a gunman on a scooter carried out a string of shootings across New York City that left one person dead and three others wounded, according to the Queens District Attorney's Office. A suspect has been arrested and charged with murder in the case.

"We have a recurring theme in the city -- illegal bikes, illegal firearms and people who pull those firearms," Chell said Tuesday.

"Our detectives up here in the Bronx will do everything they can and they will solve this case," he added.