Police believe Kristine Peralez opened fire at the Ben E. Keith Foods building on Cravens Road near Gessner early Monday morning.
Two employees were shot and Peralez died during a confrontation outside the building with police.
Fedencio Janas was shot in the leg and taken to Southwest Memorial Hermann Hospital.
The second victim, manager Francisco Reyes, was shot multiple times and died at the scene.
Peralez's father-in-law, Antonio Peralez said, "We're all devastated. All this just came as a shock to us early this morning."
RAW VIDEO: First radio calls from authorities during shooting
Peralez said he doesn't know why his daughter-in-law opened fire at the facility, "Something triggered her, something happened to her for her to act this way because it's out of character, it's not her."
Police say 20-25 people were working at the time of the shooting, including Kristine's husband of seven years. He was not injured.
Peralez said they were at the end of their shift when the shooting began.
Missouri City Police Chief Mike Berezin said, "Quite a few of the employees spoke with the shooter quite a bit during the day today."
Peralez said he noticed Kristine was sad over the weekend and seemed to be in a state of deep thought, "I'm so sorry, I'm so sorry all this happened and nobody should go through this," said Peralez.