The members of the Orthodox Shomrim group were following him in the Borough Park neighborhood Thursday night after residents called a hotline. They first reported seeing the man leering at young girls earlier in the week.
The Shomrim is a licensed, unarmed community group that works with police to keep order in several Brooklyn neightborhoods.
When confronted Thursday, police say the man got out of the car and started running. Group members forced him to the ground when he opened fire. They held him until the NYPD arrived.
Police did not release the suspect's name.
One of the Shomrim was shot in the neck, two were shot in the hand and one was hit in the stomach.