morgan radford reports. >> reporter: a somber campus, mourning the lives of four international students killed when a duck tour boat collided with their charter bus. >> i was just shocked. >> the students came to the united states for college from austria, indonesia and japan and china. >> in the beginning, some of the first responders wouldn't find out who they were because they didn't speak english. that is scary. >> reporter: today the ntsb looks into the investigation. >> we look at all aspects. we enter an investigation of this sort thinking anything is possible. let's see where the trail leads. >> the lanes on the bridge where 9.5 feet wide but the duck boat is 8.4 feet wide. but it swerved five lanes and into oncoming traffic and t-boned the charter bus. local residents have long said this bridge is an accident waiting to happen. >> we shouldn't lose people to make a change that needs to be made. >> reporter: this is the bridge where the accident actually happened. but you can see it is tricky because there are no dividers between the actual lanes. so it feels pretty narrow for t

nbc's morgan radford reports. >> just before noon a charter tour bus collided with a popular duck tour vehicle crowded with tourists. nearly 100 first responders rushed to reach the horrific scene. a triage was set up to rescue the trap and treat the injured. at least 50 people were evaluated. witnesses say the open air vehicle struck the middle of the bus, shattering the window, ripping off panels and reducing it to a twisted chouchk metal. >> shot across all three lanes at full paid and hit the side of the bus. and people in the bus flew through the front of the windshield. >> the company expressed condolences but said the cause of this accident is not known. on the bus, 45 students and employees from a local college. many of them international students getting ready to start the school year. >> we've had a terrible tragedy. a terrible loss of life and there's been injuries and our thoughts the thoughts and prayers of this city go out to even. >> duck tours is a popular tourist traction. the boat is designed to travel on roads as well as water. so it is stronger than school buses but

nbc's morgan radford has late details. >> reporter: just before noon, a charter tour bus filled with students collided with a popular duck tour vehicle crowded with tourists. nearly 100 first responders rushed to reach the horrific scene on a seattle bridge. a triage was set up to rescue the trap and treat the injured. at least 50 people were evaluated. the scene so chaotic, one victim rushed to the hospital breaking through an ongoing press conference. >> this is a very fluid situation. >> some of the challenges is the fluidity of the incident and amount of people that need our help simultaneously. >> reporter: the open-air vehicle hit the bust reducing it to a twisted chunk of metal. >> full speed hit the side of that bus. people on the bus flew through the front windshield. >> reporter: in a statement from ride the duck seattle, the company expressed condolences, but said the cause of this accident is not known. on the bus, 45 students and employees from a local college. many international students getting ready to start the school year. >> we had a terrible tragedy. there's been

morgan radford has more. >> reporter: they were celebrating their anniversary and first it was ruledccidental death. now more details about the husband's past and prosecutors say this fall is no fluke. two wives and two deadly accidents. 59-year-old harold hendorn pushed his wife to her death. he took his wife to a hiking area in 2012 to take in the romantic view of the national park and celebrate their 12th answ anniversary. he says toni plunged to her death. the autopsy report says it was an accident initially. now it could have been a lethal push by her husband. toni's autopsy files list blunt force trauma to her head, neck and chest. all leading pathologists say homicide cannot be excluded. a park map is leading to the site where toni fell. the case was written about in "people" magazine. >> it is interesting you put the map in your car and forget to take it out. >> reporter: what is more curious. hendorn's first wife mysteriously died also around the 12th anniversary. she was crushed by the car as they were changing a tire as it slipped off the jack. >> in 2012, a neighbor came

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