(Guadalupe, AZ) -- A man is under arrest in connection with a fatal shooting in Guadalupe yesterday evening. The Maricopa County Sheriff's Office says 20-year-old Phillip Valencia got into a fight with his girlfriend before grabbing a gun and charging into a birthday barbecue he just happened upon . Enriquez says Valencia opened fire at the party, striking a man and a woman. The man has died. The woman is in critical condition. Valencia was arrested at his home and has been booked into the Maricopa County jail on first-degree murder charges.