CLINTON — Two days after a man jumped from the stern of the ferry M/V Cathlamet during the 10 p.m. sailing Sunday, investigators are still trying to sort out who the man was and why he apparently leapt to his death in the frigid waters of Puget Sound.

Officials from Washington State Ferries said a walk-on passenger boarded the Cathlamet in Mukilteo on Dec. 11 and jumped off the back end of the ship as it was halfway to Whidbey Island.

The crew of the vessel immediately contacted the Coast Guard after the man went overboard, and ferry service on the Clinton-Mukilteo route was suspended for more than one hour as the Cathlamet helped search for the missing man.

Although the man apparently left a shoulder bag aboard the ferry, investigators said they had not yet identified the man.

Detective Don Cunningham with the Washington State Patrol said anyone who may have information on missing persons in the area should contact authorities.

“We really don’t have a lot right now. If the public is aware of someone who is missing and may have been in the area, that’s the kind of help we are looking for,” Cunningham said.

Rescue crews continued to search for the missing man in the waters off Whidbey Island earlier this week.

At the start, a 45-foot response boat from Coast Guard Station Seattle was brought in, and a MH-65C Dolphin helicopter from Air Station Port Angeles, to help with the search late Sunday.

Island County Fire District 3 also launched a marine vessel from Possession Point to assist with the search. Deputy Chief Mike Cotton was on the rigid-hull inflatable with two other FD3 firefighters in the waters near the Clinton Ferry Terminal by 10:20 p.m. Sunday.

Cotton said they searched until 2 a.m., until the fog crept across Puget Sound and the tide shifted north.

“With weather and resources we pulled out,” Cotton said.

The water temperature was measured at 48 degrees Fahrenheit, and authorities said hypothermia can be fatal in as little as one hour at

50 degrees. The outlook was grim as the search continued.

“We’re not necessarily looking for a person at this point, let me put it that way,” Cotton said Monday morning.

The Seattle crew was relieved by the Coast Guard Cutter Wahoo, a coastal patrol boat homeported in Port Angeles, which arrived in the waters off Whidbey Island at approximately 3 a.m. Monday.

Tom Niemeyer was on board the Cathlamet during the emergency. He and his girlfriend were coming home from a spaghetti dinner at his uncle’s house in Ballard and were in the last car to get on the ferry.

He said he often catches the 10 p.m. ferry, but this sailing soon took a twist.

“About halfway across, we heard the ding-ding-ding, ding-ding-ding,” Niemeyer recalled.

He expected a drill announcement to come over the ship’s intercom, but none did. A few minutes later, several crew members came rushing past his truck on the way to the back of the ferry.

Five minutes after the alarm sounded, as the ferry was almost to Clinton, the ship started to turn around and the ship’s captain came on the intercom.

“He said, ladies and gentlemen, we have a possible passenger overboard situation. We ask that at this time that anybody who can and will — we need everybody to go to the side of the ferry and look overboard,” Niemeyer said.

“I jumped out of my truck and went over to the side and started looking into the water.

“Everybody was out of their cars. Everybody jumped right to it,” he added. “It was crazy. We didn’t even think twice about it, we just started looking.”

Ferry riders started grabbing flashlights and went to the sides of the ship. Any place you’d look, he said, there was someone standing, looking into the dark waves.

Niemeyer grabbed his own flashlight and went to the port side of the ship. The man who was parked in front of him got out and asked, “Is this a drill?”

“I said, no, we should be looking for somebody,” he said.

The man went back to his car and pulled out a powerful flashlight, and the pair began looking together. There were 20 to 30 other ferry passengers on the same side of the ship, also looking out into the waves.

The ferry turned and started back toward Mukilteo, with the ship’s big searchlights fanning across the water.

About halfway across, the ship’s captain announced they were at the spot where the passenger may have been lost; he asked everyone on board to “keep a super sharp lookout” as the ship slowed down.

The Cathalmet crew put their small craft in the water and went out to search, Niemeyer said, and added that he didn’t see any other rescue ships arrive for at least 45 minutes into the sailing.

“We thought it was really odd. It was like, ‘Aren’t we going to get some help here?’” Niemeyer recalled.

There was a somewhat helpless feeling, he added.

“You’re looking at pitch-black water with a couple of flashlights.”

The ferry eventually began to make its way south of the Clinton terminal. Like others, Niemeyer remained at the rail of the ship, hoping to see the missing man.

Niemeyer said he was impressed by his fellow travelers, that they continued to stand along the sides of the ship, despite the cold. Niemeyer himself was wearing just a light dinner jacket.

“It was a collective, serious situation. Everybody did what they could under the circumstances.”

“I stayed out there the whole two hours we were doing circles,” he said. “Leaning over, looking over the water, looking.”

When the ferry arrived in Clinton, the captain made an announcement, asking the person who had witnessed the man going overboard to stay on the ship after it docked. The captain also asked other witnesses to step forward.

Niemeyer said before they pulled up, a ferry worker leaned in and asked each traveler if they had seen anything.

The missing man had walked aboard the Cathlamet in Mukilteo, said a spokeswoman from Washington State Ferries, and was carrying a shoulder bag. The bag was later found and given to the Washington State Patrol, which is leading the investigation.

When told the missing man was seen carrying a shoulder bag, Niemeyer instantly recalled an out-of-sorts-looking fellow who had walked aboard the vessel, but was standing on one of the auto ramps to the second level, “just looking at cars as they got on,” as Niemeyer drove aboard.

It was strange enough to mention, Niemeyer said, recalling that he and his girlfriend both wondered aloud about the man.

“What’s that guy doing?” he said they asked each other.

He wasn’t making his way up toward the passenger galley, but just stood there. He would have been in the way, Niemeyer added, if any vehicles were sent up the ramp to the upper deck.

“He had a strange look on his face, kind of vacant,” Niemeyer said, and noted he made eye contact with the man as he drove past.

Niemeyer described the man as in his late 40s. He was wearing an orange jacket and Niemeyer’s girlfriend thought he had a mustache.

When the couple got home, they were still thinking about the missing man. They decided to go out and walk along the beach.

“As strange as it sounds, the way the tides and the currents are, we were thinking, gosh, it might be a candidate for something that might end up on our beach,” he said.

He and his girlfriend bundled up, found flashlights and began to walk along the surf near their Glendale home. The tide was out, and they walked about a quarter mile each way from their home, looking. A helicopter with searchlights flew back and forth overhead.

They returned home at 4 a.m. and said they could see the search continuing out over the water.

The man-overboard incident left travelers stranded on both sides of the route for more than one hour Sunday night.

The 10:30 and 11 p.m. sailings on the route were canceled, said WSF spokeswoman Susan Harris-Huether. The Coast Guard released the Cathlamet from the search at 11:30 p.m. after nothing was found, and three final sailings made the crossing overnight.

Record writer Ben Watanabe contributed to this report.