A man has been arrested in connection with the shooting of another man driving a Hummer on the southwest side.

A man traveling east on West Irvington Road west of South Mission Road went off the street and crashed into a tree Wednesday morning.

A Pima County Sheriff's Department detective in the area working a case witnessed the crash and went to help the man, said Deputy Jesus Bañuelos, a department spokesman.

The man, who was driving a Hummer, told the detective he had been shot. The detective, who rendered aid, called for paramedics, who treated the man and took him to University of Arizona Medical Center with life-threatening injuries, said Bañuelos.

Deputies arrested Anthony Acuna, 26, in connection with the shooting. He is facing charges of aggravated assault with a deadly weapon.

The wounded man is in critical condition at UAMC.