I read a story about a woman who was walking home, along a path, from a store to her home. She fell. She used her phone to call her common-law husband for help. That was at 5:30pm; they found her body at 11pm.
He lived 40 miles away on a farm. He was called by the police at 4:30am to come to identify her body; she died from a heart attack. When he returned to his home at 9am, he checked his answering machine and heard her last message from the previous evening. She had been able to make only one phone call. If she had used that call for 911, the outcome may have been different.
When your life in on the line, be selfish and call 911 as your first call. You may not get a chance to make another.