The man, 68, waited for the woman, 42, to start the commute home from work and fired three shots that hit her "in the face and neck, causing injuries that endangered the life of the victim," says the Public Ministry (MP).
The suspect and the victim are married and have two under-age daughters, but "their relationship has been severed since mid-2020", the Faro district attorney's office said in a statement posted on its website.
The Public Ministry requested and applied to the suspect the measure of preventive detention, adds the same note.
The crime occurred at 8pm on Monday, "on the public road in the city of Portimão", according to the Judicial Police.
The man is indicted for the crime of qualified homicide in the attempted form.