know why the gunman opened fire outside the allen premium outlets. >> the big question that we are dealing with right now is what is his motive? why did he do this? well, the big question is, we don't know. >>reporter: but authorities say the attack didn't last long, thanks to the quick response of an allen police officer who stopped the shooter. >> i think within 3 or 4 minutes, the allen pd officer had neutralized the suspect. >> reporter: we understand he works in private security gigs before, did he ever work at the allen premier outlets? >> not to my knowledge. >> reporter: investigators also said they believe the shooter targeted the location but shot people at random. >> he was very random in the people he killed. it didn't matter the age, same race, or sex, and he just shot people, which is horrific in itself. >> reporter: among the people killed was 26-year-old engineer aishwarya thatikonda. for her friends and coworkers, the shock of the shooting is still hard to fathom. >> she had big dreams. she wanted to make a living in this country, to become a