Greater Manchester Police chief Michael Todd sent a series of "worrying" text messages before he was found dead in north Wales, the BBC has been told.
Mr Todd, 50, was found dead about 100m from the summit of Snowdon on Tuesday afternoon, his body covered in snow.
There was no sign of trauma on his body and the north Wales coroner said a post-mortem examination had found "no obvious cause of death".
The inquiry into his death is looking at the possibility of suicide.
Mr Todd had been off-duty on Monday and had spent the day walking in the Welsh mountains.
The alarm was raised after he sent the messages to various people, which caused concern for their safety and his own, the BBC has learnt.
The search for him began in the early hours of Tuesday but it was later in the day that hill walkers reported seeing a body near the summit of Snowdon.
His body was found on part of the mountain called Bwlch Glas at about 1500 GMT, with some of his outer clothes missing.
Sources said Mr Todd was found lying down on a sloping track next to a bottle of spirits.
Tests have found no obvious signs of trauma, suggesting he did not jump or fall to his death.
Further tests are being carried out to determine if any alcohol or drugs were in his blood.
Coroner Dewi Pritchard Jones said the post-mortem examination took place on Wednesday morning.
He added: "We're hoping to have the toxicology done by tomorrow morning."
A number of letters addressed to his loved ones have since been found but police said no letters were found at or near the scene of his death.
An inquest into Mr Todd's death is to open on Thursday.
The father-of-three, who lived in a flat in Manchester city centre, was known to have previously separated from his wife.
The BBC has also learnt that Mr Todd suffered from bouts of depression, and had previously threatened suicide.
On Wednesday, a series of front line officers gave their tributes to their former chief, while Assistant Chief Constable David Thompson described Mr Todd as one of the "world's best police leaders".
"He put the Great back into Greater Manchester by his charismatic leadership, the trust and confidence he placed in all our staff and the new and innovative thinking he brought to the challenges we face and, of course, his unique sense of fun," said Mr Thompson.
He said crime was down in Greater Manchester since 2002 when Mr Todd joined the force, which he had turned into an "effective crime fighting organisation".
But he added: "As a force we feel a huge loss with Michael, but it pales into insignificance to the loss his family are facing. And we're offering them all the support we can at a really terrible time for them."
One officer - 32-year-old Pc Geoffrey Hince - described Mr Todd as a great leader whom he was honoured to work for.
"He was just a copper's cop. He wanted to get out there, he wanted to feel people's collars, he got out there in the thick of it," said Pc Hince.
Books of condolence have been opened at Manchester Cathedral and online at the Greater Manchester Police website.