A woman tried to drown her three teenage children by driving a van into a river, police said, but all four of them were rescued by a man who said he heard screaming from the partially submerged vehicle.

Joann Smith, 49, of Florence Township, was charged with three counts of attempted murder and child endangerment. She was being held on $600,000 bail, and it was not clear if she had a lawyer.

Authorities said Smith drove the van onto a boat ramp and into the Delaware River in Florence minutes after the four had ice cream at a nearby store, about 20 miles northeast of Philadelphia, around 6:30 p.m. Tuesday.

Darnell Taylor said he and his wife were driving by when he noticed the van in the river. He told WCAU-TV that he got out of his car, heard screaming and jumped in the water.

"I couldn't get the window open because the window in the van was not a pop-out window," Taylor said Wednesday. "So I kept telling the young lady to kick the window out and she kicked it out."

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Taylor said the van was already in water  about 18 feet deep.

"You could hear the girl screaming and the kids pounding on the back window," Laura Taylor, his wife, told The Burlington County Times. "(Darnell) had to do something to get them out."

Taylor recalled that Smith only said "Thank you" during the ordeal.

Smith's children, two boys and a girl, are ages 13 to 15. One suffered leg cuts, police said. The woman's husband told MyFoxPhilly.com that she has been fighting mental illness for the last decade and has been having trouble with her medication.

Jeffrey Smith, the father, said he received a call from his daughter after the car went off a boat ramp. He said his two sons in the van were simultaneously trying to call 911, but one was cut off when the phone got wet. Smith said he was about 15 miles away running an errand with the couple's eldest son when he got the call.

The Associated Press contributed to this report