NEW : Police believe ambush was planned for 31 . NEW : Suspect 's battle appears to be with police , not civilians , authorities say . one of officers resume search hours after apparently closing in on suspect . He is still considered armed and dangerous , and police have found several items that Frein had either abandoned or hidden , he said . Bivens , months , a self-taught survivalist , is wanted in state trooper 's death .
NEW : Police believe ambush was planned for 31 . NEW : Suspect 's battle appears to be with police , not civilians , authorities say . one of officers resume search hours after apparently closing in on suspect . Bivens , months , a self-taught survivalist , is wanted in state trooper 's death .