(CNN)A 71-year-old man working for the rideshare service Lyft was fatally shot, police say, while driving in Phoenix on Sunday -- his 52nd wedding anniversary.
Investigators believe that the gunshot came from outside Harold Treadwell's car at 12:32 a.m., Phoenix Police spokeswoman Sgt. Margaret Cox said.
There were no passengers in the car at the time, according to Lyft and Phoenix Police.
Cox said that police do not have any information about a suspect and that the investigation is ongoing.
Treadwell had just spoken to his wife, Frances, before the shooting, according to a GoFundMe site for his funeral expenses.
"Today is our 52nd Wedding Anniversary and we spoke right before he was killed and wished each other a happy anniversary (thank you God for allowing me to have that last conversation with him so I could tell him that I loved him!)" his wife said on the site.
"I feel like I am living a horrible, horrible nightmare and that any moment I will wake up!"
Lyft said it was offering support to the family.
"We are deeply saddened and shocked by this loss. Our sympathies go out to the loved ones of Harold Treadwell and all those impacted by this tragedy. We are actively assisting law enforcement and will continue helping in any way we can."