The helicopter flying basketball great Kobe Bryant, his 13-year-old daughter and seven others reportedly encountered heavy fog in the skies of southern California before the deadly crash Sunday that killed everyone on board.

Reports from The Washington Post and CNN indicated that visibility was so poor on the day of Bryant’s crash that police were forced to ground their own helicopters amid the effort to search for survivors.

Weather reports indicated that a low cloud cover was present on the day of the crash, further complicating flying. Bryant’s pilot was operating the craft under a special clearance for poor weather conditions, but reportedly had experience in such situations.

National Transportation Safety Board (NTSB) officials reportedly said in Tuesday a press conference that the last transmission from the pilot indicated that the craft was climbing to avoid cloud cover.

Jerry Kidrick, a professor of advanced helicopter operations at Embry-Riddle Aeronautical University, told the Post that the pilot’s rapid ascent shortly before the crash indicated that the pilot could have been disoriented or panicking.

That pace at which he climbed indicates hes trying to get out of there, or he got spatially disoriented, Kidrick told the newspaper. Thats a very common thing [investigators] find post-crash; the pilot makes rapid corrections and rapid maneuvering…It appears something went wrong.