A private helicopter with five people on board crashed Thursday into Hawaii's Pearl Harbor, leaving a teenage passenger in critical condition, officials said.

The Bell 206 aircraft made a hard landing and sank near the Pearl Harbor Visitor Center, a popular tourist destination on Oahu, U.S. Navy spokeswoman Agnes Tauyan said.

The names of the five people on board were not immediately released.

"We are told bystanders jumped in to help rescue these patients from the water," said Shayne Enright, spokeswoman for Honolulu Emergency Services Department.

The helicopter crashed about 20 feet offshore, right next to the visitor center's lawn, said tourist Justice Winrich of Madison, Wisconsin. She watched as it "plopped down" into the water.

"I saw it like as it was coming in, and it looked pretty normal. It didn't look like it was shaking or anything," Winrich said. "It just started like getting really close this way and started going down." She thought it was strange that the helicopter was that close to people.

As it got closer to the water, she saw some dark some coming out of the back of the helicopter, and it started shaking slightly.

Winrich saw three people get out of the helicopter immediately and start swimming to shore.

"I was like, oh my God, I can't believe this just happened. It was crazy," she said. "You go on vacation and you never think you're going to see something like that."

Local author Allan Seiden was signing books at the visitor center when someone told him a helicopter crashed. He rushed over to where people were gathered, but by then the helicopter wasn't visible.

"I think it sunk instantly," he said.

Seiden watched as the helicopter's occupants— including a man in a neck brace— were carried away on stretchers. "People were very calm. ... You could tell everyone was very shocked," he said.

Federal records show the helicopter is registered to Jeffrey Gebhard of Kailua, Hawaii. He couldn't immediately be reached for comment.

The Navy said in a statement that the helicopter reportedly belongs to Genesis Aviation. The company website says it conducts helicopter tours of Oahu.

Honolulu paramedics treated the 16-year-old passenger and took him to a hospital in critical condition, Enright said.

A 45-year-old woman and a 50-year-old man were taken to the hospital in stable condition. Details on the two other people on board, including the pilot, weren't immediately available.

Operations at the visitor center, including visits to the nearby USS Arizona Memorial, were suspended until further notice, the Navy said. The memorial honors the 1,177 sailors and Marines killed on the ship in the Dec. 7, 1941, attack by Japan.

Federal Aviation Administration investigators were on their way to the crash site. A National Transportation Safety Board investigator was expected to arrive Friday.

It was the second major crash this year involving helicopters on Oahu.

Twelve Hawaii-based Marines were killed when two helicopters military crashed during nighttime training on Jan. 14. Both aircraft were CH-53E Sea Stallion helicopters that were part of Marine Heavy Helicopter Squadron 463.