BIG BEAR LAKE, Calif. — Clear skies allowed aircraft with heat-sensing technology to aid scores of officers searching in the San Bernardino Mountains for Christopher Dorner, the former Los Angeles police officer suspected of killing three people in a vengeance-fueled rampage aimed at those he blames for ending his career.
Two sheriff’s choppers flew low over the forest Saturday as SWAT teams fanned out to look for tracks in the foot of snow that fell overnight.
It was the third full day of the massive hunt for Dorner. He has continued to elude authorities whose last clue to his whereabouts was a burned-out pickup truck found Thursday in this ski resort town.
Authorities were hopeful that clearer skies would allow aircraft to help them find Dorner.
SWAT teams in camouflage went door to door examining vacant cabins, aware that they could be walking into a trap set by the well-trained former Navy reservist who knows their tactics and strategies.
‘‘He can be behind every tree,’’ said T. Gregory Hall, a retired tactical supervisor for a special emergency response team for the Pennsylvania State Police.
Thousands of heavily armed police remained on the lookout across California, Nevada, Arizona, and northern Mexico for a suspect bent on revenge and willing to die.
Police said officers were still guarding more than 40 people mentioned as targets in a rant they said Dorner posted on Facebook. He vowed to use ‘‘every bit of small arms training, demolition, ordnance and survival training I’ve been given’’ to bring ‘‘warfare’’ to the LAPD and its families.
In his online rant, Dorner berated authorities.
‘‘Any threat assessments you generate will be useless,’’ it read. ‘‘I have the strength and benefits of being unpredictable, unconventional, and unforgiving.’’
Without the numbers that authorities have, Dorner holds one advantage: the element of surprise.
Authorities said they do not know how long Dorner had been planning the rampage or why he drove to the San Bernardino Mountains. Property records show his mother owns undeveloped land nearby, but a search of the area found no sign of him.
It was not clear if he had provisions, clothing, or weapons stockpiled in the area. Even with training, days of cold and snow can be punishing.
‘‘Unless he is an expert in living in the California mountains in this time of year, he is going to be hurting,’’ said former Navy SEAL Clint Sparks, who now works in tactical training and security.
‘‘Cold is a huge stress factor. . . . Not everybody is survivor-man.’’