Two teens who led police on a manhunt through the Canadian wilderness this summer admitted in videos recorded on the run to killing an Australian man, his American girlfriend and a Canadian botany professor, authorities said on Friday.But an exhaustive investigation failed to turn up a motive, the Royal Canadian Mounted Police (RCMP) told a televised news conference."The murders appear to be random and crimes of opportunity, with no known motive," said RCMP Assistant Commissioner Kevin Hackett, adding that no other suspects are being sought."In the videos, the suspects took responsibility for all three murders, they indicated no remorse for their actions, as well as their intentions to potentially kill others."Childhood friends Kam McLeod, 19, and Bryer Schmegelsky, 18, had been tracked over three weeks from westernmost British Columbia more than 3 000km east to Manitoba province.A massive search across harsh terrain - inhabited by wolves and bears and infested with mosquitoes - involved tracker dogs, a drone, and search planes equipped with infrared cameras.Authorities eventually found the teens' bodies in dense brush alongside two rifles and a cellphone used to record six videos.In one recording, according to an RCMP report, "Schmegelsky states that they are responsible for the three murders" of Australian Lucas Fowler, American Chynna Deese and Canadian Leonard Dyck."They were going to march to Hudson Bay where they planned to highjack a boat and go to Europe or Africa," the report said. "These videos do not contain information regarding the motive behind their actions nor do they provide specifics regarding the murders." Police have not released the videos but gave a detailed account of them.Fowler and Deese had been touring Canada when they were shot and killed near Liard River Hot Springs nature park in British Columbia in mid-July.Initially, McLeod and Schmegelsky were reported missing themselves after their car was found torched, but police then discovered the third body, and the teens were named as suspects.They had told their families they were heading to northern British Columbia and the Yukon to find work when they left Port Alberni on Vancouver Island.They shot Fowler and Deese using guns legally purchased days earlier before continuing north to the Yukon, then headed back south a few days later, police said in the 13-page report.They were apparently having car troubles when they came across Dyck outside of Dease Lake, robbed and killed him and burned their own vehicle to cover up evidence.On August 7, police closing in on the pair found items linked to the suspects on the shores of the Nelson River in Manitoba, as well as a battered aluminum boat.Their remains were soon found nearby, about eight kilometers from a burned-out stolen vehicle belonging to one of the victims.It is believed McLeod shot Schmegelsky and then himself in a suicide pact.